Preheat the oven to 325°F/160°C and line an 8x8 pan with parchment paper and set aside.
In a bowl, whisk together cocoa powder, brown sugar, and white sugar.
1/2 cup white sugar, 1/2 cup brown sugar, 3/4 cups cocoa powder
Add in the melted butter and continue whisking. It's fine if the mixture is grainy.
1/2 cup butter
Slowly add in 1 egg at a time. Add in the vanilla extract with the second egg. The mixture will come together smoothly.
2 eggs, 2 tsp vanilla
Whisk in the flour until there are no streaks showing. The batter will be thick. Don't overmix! Fold in the dark chopped chocolate.
3/4 cups flour, 1/2 cup dark chocolate
Add half the batter into the prepared pan and spread evenly. If it's to thick to spread with a spatula, use the back of a spoon or your hand. Make sure the entire bottom of the pan is covered evenly.
Lightly press down and create dips in 6-8 places in the brownie batter. Make sure the parchment isn't showing at the bottom though! Scoop a tablespoon of cookie butter into each dip, and lightly spread it around (About 2/3 cups total).
1 cup Biscoff
Add the rest of the brownie batter on top. Spread gently, making sure not to move the Biscoff spread underneath.
5 Biscoff cookies
Top off with swirling the spread into the batter and some crushed cookies (About 1/3 cup total).
1 cup Biscoff
Bake for 20-22 minutes or until a toothpick inserted comes out crumbly. Make sure when you're inserting the toothpick it's into the actual batter, and not the cookie butter.
Allow to cool completely, slice, and enjoy!