Preheat your oven to 180C/160C Fan, and line a 9x9" square tin with parchment paper.
Melt the dark chocolate with the butter and leave to cools lightly whilst you make the rest of the brownies!
Whisk together the eggs and sugar until really thick and mousse like - it will double in volume, be a lot paler, and leave a trail for a couple of seconds before disappearing when done!
Fold the chocolate/butter mix into the eggs/sugar mix carefully - don't deflate the eggs by being careless!
Add in the plain flour and cocoa powder, and fold that in as well.
Add in the chocolate chips and Biscoff biscuits, fold through, and pour into the tin.
Using two teaspoons, spoon dollops of Biscoff spread onto the top of the brownies - I do about 15 or so dollops!
Bake the brownies in the oven for 30-35 minutes, or until baked through. I tend to check them after 25 minutes as some ovens are hotter than others!
Leave the brownies to cool fully in the tin!
Notes
You can find the Biscoff spread with the Nutellas/jams in supermarkets!
This recipe would work well with Nutella or peanut butter in place of the Biscoff spread if you preferred!
These will lasting an airtight container for 4-5 days!
If they are still gooey after the time, bake for a further few minutes and then leave to cool fully. Refrigerate before cutting to make it easier!
If your brownies are taking an endless amount of time to bake - the mixture was probably over mixed, or not moussey enough.
Do NOT use milk chocolate in place of the dark - it doesn't taste too dark, it just really helps bake the perfect brownies!