Line a 20cm/8" square tin with greaseproof paper for easy removal
Toast your oats on a low heat for 8-10 mins, stirring every minute or so until they smell almost popcorn-like and have turned slightly golden. Then place into a large bowl along with your crushed biscuits
Melt your butter, sugar, vanilla, and golden syrup
Pour this over your oat and biscuits, and mix to incorporate
Transfer to your lined tray, spread out with a spatula and lightly press down, don't press too firmly
Bake for 14-15 mins for soft chewy flapjacks, or 17-18 mins for crispy. Bare in mind these will be soft when they come out of the oven, wait for them to cool and firm up
Place your biscoff spread into the microwave for 10s increments until pourable, drizzle this over your flapjacks
Do the same with your chocolate and drizzle once again
Place the flapjacks into the refrigerator for 15-20mins or until the top has slightly set
Notes
You can substitute any syrup with the golden syrup, but the golden syrup flavour is synonymous with flapjacks in my opinion!