This delicious easy vanilla custard slice consists of a delightful creamy vanilla custard filling sandwiched between two layers of puff pastry and topped off with a simple icing glaze. A true classic!
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To say I was happy to see custard squares freely available in New Zealand when we moved here is an understatement. Seeing this classic dessert that I had grown up with sort of made walking around the foreign shops a little less daunting.
That being said, most custard squares or vanilla custard slices here in Christchurch are covered with a fairly thick layer of icing and topped off with desiccated coconut. Which is not 100% what I'm used to and still delicious!
In Australia, custard slices are typically referred to as a "vanilla slice".
With Vanilla Custard Slices/Squares not only being part of my childhood but seemingly popular here in New Zealand and Australia, it was about time I put a recipe on here!
Why You Will Love This Vanilla Custard Slice
- It's fairly quick and easy to make!
- This recipe uses store-bought puff pastry which makes this recipe even easier than anticipated.
- The thick custard centre is foolproof!
- The delicious creamy custard filling is sandwiched between two delicious layers of puff pastry and topped off with a nice sweet glaze.
- Bring back all the nostalgic feelings of your childhood.
Ingredients
Here are the ingredients, notes, and possible substitutions for the vanilla custard slice/square. Please see the recipe card for quantities.
Store-bought puff pastry - I used Edmonds, as I think it's the best store-bought version we can get our hands on in New Zealand. But honestly, you can use whatever brand of puff pastry you prefer. I also like getting the ready-rolled sheets for ease of use.
Milk - I used whole milk or regular milk for this custard filling. There is only milk in this recipe and no cream. Milk is also used to make the vanilla icing glaze.
Butter - as a substitute for other recipes that may call for cream. And adds a bit of decadence to the custard filling.
Custard Powder is found commonly here in New Zealand (my favourite being the Edmonds Custard Powder), as well as in Australia, the UK and South Africa. Custard powder is a mix of cornstarch (cornflour in UK, Aus, NZ and SA), and custardy flavours. This is typically cooked together with milk and sugar to make an instant custard.
Eggs add a bit of flavour and also help set the custard filling.
Sugar - plain, regular white granulated sugar to sweeten the custard filling. White sugar does not compete with the custard flavourings which are subtle.
Vanilla extract to flavour the custard filling and the icing glaze.
Icing sugar/powdered sugar/confectioner's sugar for the icing glaze.
Room Temperature Ingredients
Use room temperature ingredients! Using room temperature ingredients ensures that ingredients in the batter or dough will incorporate easier. Take note that room temperature refers to around 20°C/68F.
- Place eggs into warm water for about 10 to 15 minutes to bring them to room temperature quickly.
- To bring butter to room temperature quickly, cut the butter into cubes and zap in the microwave at 20% power in 10-second intervals. Or place the cubes in a bowl over warm water (such as with a double boiler) over low heat for 1 minute!
- Milk, buttermilk, and cream can be brought to room temperature by zapping in the microwave at 20% power in 10-second intervals. Or on a low heat for a minute or two swirling every 10-15 seconds.
Weighing & Measuring Ingredients
Weighing ingredients with a kitchen scale is more accurate than using measuring cups. All my recipes are developed and tested using grams only.
However, I have activated the metric-to-cup conversions. Simply click on "cups" or "metric" for your preferred measurements. For these conversions, cups are equal to 240 millilitres/8 fluid ounces, tablespoons are 15 milliliters and teaspoons are 5mL.
How to Make Vanilla Custard Slices
Step 1 - Prep the cake tin
Line an 8"x8" square cake tin either with tin foil or baking paper with an overhand. This allows the custard slice to be removed once it has been set much easier. Set the cake tin aside.
TIP - before lining the cake tin, it may help to cut out a piece of baking paper the size of the inside of the tin. Then place this template on the top of the pastry once it has baked to make trimming to size easier.
Step 2 - Roll out the pastry
Preheat the oven to 180°C/350F. Line two baking sheets with baking paper. If rolling out the pastry, roll it out to about 5mm thick, and at least an inch or 2.5cm wider than the cake tin being used for the slice.
Step 3 - Bake the pastry
Place the pastry on the line baking sheets. Prick the pastry all over with a fork, about 2cm apart. Bake the pastry for 25 to 30 minutes or until golden brown. Remove the pastry from the oven and allow it to cool.
NOTE - Pricking the pastry is essential in allowing the pastry to rise evenly during the baking and also keeps the pastry from rising too much.
Step 4 - Trim the pastry
Once the pastry has cooled, trim the pastry to fit inside the cake tin using a serrated knife. Place one of the pastry sheets at the bottom of the cake tin. Keep the second aside while making the custard filling.
Step 5 - Heat the milk
Gather all the ingredients for the custard filling. In a medium-large sized saucepan, bring the milk and vanilla extract to a boil, this will take a few minutes.
TIP - prepping ingredients before cooking the custard filling is important as once the cooking process begins, it can go really quickly.
Step 6 - Combine the eggs, water and custard powder
While the milk is heating, whisk together the eggs and water until well combined. Then add in the custard powder and whisk until there are no more lumps.
NOTE - this order of adding ingredients is important. I've found that adding cornstarch to the eggs first can result in the eggs and cornstarch making a cement-like mixture.
Step 7 - Add in the sugar
Once the milk has come to a boil, remove from the heat, add in the sugar and whisk until dissolved.
Step 8 - Add in the custard egg mix
While still off the heat, slowly pour in the egg mixture while whisking consistently. Once the egg mix has been completely mixed in.
Step 9 - Cook the custard
Place the custard mix back on the heat and cook the custard while continually whisking until it is very thick, about 7 to 10 minutes of cooking.
Step 10 - Add the butter
Take the custard off the heat and add the butter in small chunks, whisking until the chunk is completely incorporated before adding the next chunk of butter.
Step 11 - Assemble the slice
Pour the cooked custard over the pastry in the cake tin, and smooth out with a spoon or offset spatula. Then place the second layer of pastry and gently press it into the custard. Allow it to cool at room temperature for an hour before placing it in the fridge to set for 3 to 4 hours or overnight.
TIP - The custard filling needs time to set, removing it from the tin before it has completely cooled and set will result in a delicious mess.
Step 12 - Make the icing
Once the custard slice has set, whisk together the icing sugar, vanilla and milk (start with 4 tablespoons and increase when needed) until you have a nice pourable glaze. Pour over the top of the custard slice and allow to set for an hour.
Step 13 - Enjoy the slice
Using the overhangs, remove the slice from the tin and slice using a serrated knife.
Pro Tips for this Recipe
Gathering all the ingredients for the custard and measuring them before you start making the custard is key to a smooth, creamy custard filling.
Ovens
The temperatures stated are for conventional ovens. For convection, fan-forced, fan-assisted, or air-fryers, the temperature must be reduced by 20°C/25°F.
For baking, make sure the oven is fully preheated, and that the rack is in the middle of the oven. Open the oven as little as possible. For best baking results use an oven thermometer.
Remember that all ovens work slightly differently and bake times may need to be adjusted for your specific oven.
Bakeware
Metal bakeware is superior when it comes to baking biscuits, cookies, brownies, muffins and quick bread, scones, cakes. These heat up and cool down faster than glassware. Glassware is heavier, heats up and cools down slower than metal and is more suited for bread puddings, pies, crisps, crumbles and cobblers.
Storage and Freezing
These custard slices or squares must be stored in an airtight container in the fridge for up to 3 days.
Custard Slice FAQ
Yes BUT then I would add in an extra 3 egg yolks, and use a vanilla bean paste (add in an extra teaspoon too) to up the flavour in the slice. Otherwise, the slice may be a bit meh in the flavour department.
There are a few ways to tackle this delicious treat.
1) turn it on its side and just take out a bite.
2) Just embrace the messiness and chomp down on the slice
3) use a serrated knife and cut small bite-sized squares
4) pull the bottom and top apart and enjoy each slice of pastry separately
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Recipe Card
Vanilla Custard Slice
Equipment
- 8x8 Inch (20x20cm) Square Cake Pan
Ingredients
- 300 grams puff pastry plus or minus
- 750 mL milk
- 2 teaspoons vanilla extract
- 150 grams white granulated sugar (caster/granulated)
- 3 eggs (medium/large/size 6)
- 125 mL water
- 60 grams custard powder
- 60 grams butter
- 240 grams icing sugar (powdered or confectioners sugar)
- 3-6 tablespoons milk
- 1 teaspoon vanilla extract
Instructions
- Line an 8"x8" square cake tin either with tin foil or baking paper with an overhand. This allows the custard slice to be removed once it has been set much easier. Set the cake tin aside.
- Preheat the oven to 180°C/350F. Line two baking sheets with baking paper. If rolling out the pastry, roll it out to about 5mm thick, and at least an inch or 2.5cm wider than the cake tin being used for the slice.300 grams puff pastry
- Place the pastry on the line baking sheets. Prick the pastry all over with a fork, about 2cm apart. Bake the pastry for 25 to 30 minutes or until golden brown. Remove the pastry from the oven and allow it to cool.
- Once the pastry has cooled, trim the pastry to fit inside the cake tin using a serrated knife. Place one of the pastry sheets at the bottom of the cake tin. Keep the second aside while making the custard filling.
- Gather all the ingredients for the custard filling. In a medium-large sized saucepan, bring the milk and vanilla extract to a boil, this will take a few minutes.750 mL milk, 2 teaspoons vanilla extract
- While the milk is heating, whisk together the eggs and water until well combined. Then add in the custard powder and whisk until there are no more lumps.3 eggs, 125 mL water, 60 grams custard powder
- Once the milk has come to a boil, remove from the heat, add in the sugar and whisk until dissolved.150 grams white granulated sugar
- While still off the heat, slowly pour in the egg mixture while whisking consistently. Once the egg mix has been completely mixed in.
- Place the custard mix back on the heat and cook the custard while continually whisking until it is very thick, about 7 to 10 minutes of cooking.
- Take the custard off the heat and add the butter in small chunks, whisking until the chunk is completely incorporated before adding the next chunk of butter.60 grams butter
- Pour the cooked custard over the pastry in the cake tin, and smooth out with a spoon or offset spatula. Then place the second layer of pastry and gently press it into the custard. Allow it to cool at room temperature for an hour before placing it in the fridge to set for 3 to 4 hours or overnight.
- Once the custard slice has set, whisk together the icing sugar, vanilla and milk (start with 4 tablespoons and increase when needed) until you have a nice pourable glaze. Pour over the top of the custard slice and allow to set for an hour.240 grams icing sugar, 3-6 tablespoons milk, 1 teaspoon vanilla extract
- Using the overhangs, remove the slice from the tin and slice using a serrated knife.
Notes
- Before lining the cake tin, it may help to cut out a piece of baking paper the size of the inside of the tin. Then place this template on the top of the pastry once it has baked to make trimming to size easier.
- Pricking the pastry is essential in allowing the pastry to rise evenly during the baking and also keeps the pastry from rising too much.
- Prepping ingredients before cooking the custard filling is important as once the cooking process begins, it can go really quickly.
Nutrition
Nutrition information is an estimate. If scaling the recipe remember to scale your cook and bakeware accordingly. All temperatures stated are conventional, unless otherwise stated. Recipes tested in grams and at sea level.
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