Preheat your oven to 350°F (175°C). Line the baking pan with parchment paper, ensuring it covers the bottom and sides.
Melt and Mix:
In a large saucepan over low heat, melt the butter, Biscoff spread, brown sugar, and golden syrup together, stirring until the mixture is smooth and well combined.
Combine with Oats:
Remove the saucepan from heat. Stir in the rolled oats and a pinch of salt, mixing thoroughly until the oats are fully coated in the Biscoff mixture.
Bake:
Transfer the mixture to the prepared baking pan, spreading it evenly and pressing down firmly with the back of the spoon or spatula.
Bake in the preheated oven for 20-25 minutes or until golden brown around the edges but still slightly soft in the middle.
Cool and Slice:
Allow the flapjacks to cool in the pan for about 15 minutes, then lift out using the parchment paper and cool completely on a wire rack. Once cooled, drizzle with additional Biscoff spread and sprinkle crushed Biscoff cookies on top if desired. Cut into squares or bars.
Notes
Smooth Drizzle: Gently warm the Biscoff spread for the drizzle to make it easier to work with, achieving a smooth, even layer.Even Pressing: Use a flat-bottomed glass to press down the flapjack mixture in the pan evenly, ensuring consistent thickness and texture.Cool Completely: Ensure the flapjacks are completely cooled before slicing to get clean cuts and maintain their shape.Storage: Store in an airtight container to keep them chewy and delicious for up to a week.