Preheat the oven to 180°C (350°F) and line an 9" baking tin.
Melt the butter and mix the with brown sugar.
Add the eggs and vanilla and beat in.
Stir in the flour and baking powder until all combined.
.Stir in all the white chocolate chips and then pour into the prepared tin.
Dollop the Biscoff spread over the blondie and lightly swirl through. Break the cookies into pieces and place over the top.
Bake for 25-35 minutes until the skewer inserted comes out with crumbs attached.
Will be slightly under baked but that's how it should be.
Allow to cool before slicing and serving. Store in an airtight container for up to a week,
The bake time can vary so I like to check mine from 25 minutes onwards until they are baked to how I like them. I like mine slightly under baked in the middle but others like them more 'cakey' which happens when they are slightly over baked.
If you're still not sure whether the blondies are done. Once they have been baking for 25-30 minutes, let them cool completely and then place them in the fridge to firm them up.