These classic flapjacks come out chewy in the middle with lightly caramelised edges every single time. Just five ingredients, one saucepan, and about 30 minutes stand between you and a tin full of buttery, golden, sticky oat bars.
Preheat your oven to 170°C fan / 190°C / Gas Mark 5. Line a 20x20cm square baking tin with baking parchment, bringing the paper up the sides.
Add the butter, brown sugar, and golden syrup to a large saucepan over a low heat. Stir gently until the butter has fully melted and the sugar has dissolved completely. Do not let the mixture boil.
Remove the pan from the heat. Stir in the salt, then add the rolled oats and jumbo oats in two batches, mixing well after each addition until every oat is evenly coated.
Tip the mixture into your lined tin. Press down firmly and evenly with the back of a large spoon or a spatula — really compact it into the tin, right to the edges and corners.
Bake for 18–20 minutes until the edges are golden brown. The centre should still look pale and slightly soft — this is correct. Do not wait for the top to fully brown.
Remove from the oven and leave to cool in the tin for 10 minutes. Use a sharp knife to score the surface into 16 bars (4 cuts x 4 cuts), but do not cut all the way through yet.
Leave to cool completely in the tin — at least 1 hour — before cutting through fully on your score lines and removing from the tin.
All temperatures stated are for conventional ovens. Decrease the temperature by 20°C/25°F or gas mark 1 for "fan" or air-fryers.