Preheat your oven to 180°C (gas mark 4, 350°F) and line a 9″ Square baking tray with parchment paper.
Melt the butter and chocolate in a microwavable-safe bowl for up to 2 minutes and leave aside to cool down.
Place the eggs and caster sugar into a large mixing bowl. Using an electric whisk, whisk the mixture until it becomes pale and frothy.
Pour the cooled melted butter and dark chocolate mixture into the whisked eggs and sugar. With a spatula, fold the mixture together until combined.
Sift plain flour and cocoa powder into the mixture, then fold gently with your spatula until evenly combined.
Once combined, crumble the Lotus Biscoff biscuits and pour into the brownie mixture.
Fold the mixture until the Biscoff biscuits are evenly distributed throughout the brownie mixture. Pour the mixture into a lined baking tray and spread evenly using a spatula.
Place spoonfuls of Biscoff spread on top of the brownie mixture, using a skewer create a marble pattern. See the video below on how I did this.
Bake in the oven for 30 to 35 minutes for gooey and fudgy delicious brownies. You’ll find that the edges are set but the middle is a bit wobbly. Leave the brownies to cool down for around an hour before cutting.