Preheat the oven to 180 degrees C in a fan-assisted oven. Grease or line a 9x9 baking tin or silicone tray with baking paper.
In a large mixing bowl, add the melted butter and the two sugars and whisk until smooth with an electric mixer.
Add in the apple sauce, milk and vanilla extract and beat again until combined and smooth.
Sieve in the plain flour and corn flour, mix with a large metal spoon until a thick blondie mixture is created.
Add in the white choc chips and fold.
Spoon the mixture into the tin and spread until even. Melt the Biscoff spread in the microwave for 20-30 seconds and pour on top of the blondie mixture. Lightly swirl using a toothpick or skewer.
Sprinkle on the chopped Biscoff Biscuits. Place in the oven for 30-35 minutes, the middle still might be wobbly but this will continue to bake in the tin.
Leave to cool in the tin and put in the fridge for 1 hour