Preheat the oven to 180℃ and line a baking tin with baking paper
Make the egg replacer and set aside.
In a separate bowl, mix the caster sugar, melted butter, vanilla extract, cocoa powder, salt and baking powder. Once combined stir in the egg substitute.
Fold in the flour, then add in melted dark chocolate, mix well.
Pour mixture into the tin.
Microwave the Biscoff spread for 10-20 seconds until it’s soft and runny. Pour the Biscoff spread over the batter and run a toothpick or a knife through the mixture a few times to marble the mixture.
Bake for around 15-20 minutes. Set timer for 15 and check. If the toothpick/knife comes out clean they are good to go. If you want a gooey texture take them out earlier than later.
Cool completely before cutting into squares.
Enjoy!