Preheat the Oven
Preheat your oven to 180°C / 350°F / Gas Mark 4.
Grease and line a 20cm (8-inch) square baking tin with parchment paper.
Prepare the Brownie Batter
Melt the butter and dark chocolate together in a heatproof bowl over simmering water, stirring until smooth.
In a separate bowl, whisk together eggs and sugar until light and fluffy.
Gently fold the melted chocolate mixture into the egg mixture.
Sift in the self-raising flour and fold gently until just combined.
Add the Biscoff Elements
Pour half of the brownie batter into the prepared tin.
Warm the Biscoff spread slightly and drizzle half over the brownie batter.
Sprinkle crushed Lotus Biscoff biscuits over the top.
Pour the remaining brownie batter over the top and smooth it out.
Drizzle the remaining Biscoff spread on top and swirl with a knife for a marbled effect.
Bake
Bake for 20 minutes, or until a skewer inserted comes out with a few moist crumbs.
Remove from the oven and let cool completely in the pan before slicing.
Serving & Storage
Slice into 12 squares and serve at room temperature or slightly warmed.
Store in an airtight container at room temperature for 2-3 days, refrigerate for up to 10 days, or freeze for up to a month.
To reheat, warm in the microwave for 20 seconds.