Place the oven rack in the middle of the oven. Preheat the oven to 200°C/390°F.
Line two large baking trays with baking paper. A half sheet (40cm x 28cm or 16"x11") is the perfect size for a roll of pastry. If using a quarter sheet, the pastry will need to be divided in half for each baking tray.
Crack open an egg, add in a tablespoon of water, and beat until the egg is well mixed. Set aside.
1 egg, 1 tablespoons water
Unroll the puff pastry. Using a ruler and knife or bench scraper, measure and cut out 10cm x 10cm (4" x 4").
350 grams ready-rolled puff pastry
To shape the pastries, gently fold the pastries from one corner to the other to make a triangle. Using the ruler, measure a border of 1.5cm. Cut from the long side of the triangle up the corner leaving the corner intact.
Gently open the folder over the triangle. Using a form, prick the center square. This will prevent the center from puffing up too much during baking. Brush the entire top of the pastry with the egg mixture.
Place about a tablespoon of jam in the center of the pastry. Then fold the left cut corner side over to the opposite side and tuck under the right corner while pulling it to the left. Press down gently and brush the edges with the egg wash.
10 tablespoons jam
Sprinkle the almond slices over the jam and pastry edges. Bake for 20 to 25 minutes or until the pastry is puffed up and golden brown. Remove from the oven and allow to cool.
¼ cup almonds
In a small bowl, combine the icing sugar, lemon juice, and water to form a glaze. Once the tarts have cooled down, drizzle the glaze over the tarts. Serve and enjoy. This is an optional extra step and can be left out.
½ cup icing sugar, 1-2 tablespoons lemon juice or water