Preheat the oven to 160°C.
Melt the butter in the microwave, then mix in the sugar, followed by the eggs.
Gently mix in the flour, followed by the white chocolate chips/chunks.
Pour the batter into the baking tin and spread evenly to the edges.
Dollop alternate spoonfuls of Biscoff and Nutella on the surface of the batter and place in the oven for 10 minutes to soften the spreads.
Take the blondies out and swirl the spreads into each other using the toothpick/fork. Then return to the oven for a further 15 minutes of baking.
Allow to cool before slicing and serving.