1-Press a large piece of parchment paper: Press a large piece of parchment paper into a square metal 8×8 baking pan (see notes below) and crease the bottom edges so when you take it out you can see the outline of the size of the pan. Evenly spread the cookie butter inside the creased edges, then chill it in the freezer until firm. I recommend checking to make sure the layer is completely firm before starting the batter!
2-Line the baking pan with parchment paper: Line the baking pan with parchment paper to hang off all four sides for easy removal. Then preheat the oven to 350 F/180 C.
3-Whisk together the sugar, eggs, and vanilla: Whisk together the sugar, eggs, and vanilla extract until well combined.
4-Melt the butter and chocolate chips together: Melt the butter and chocolate chips together until smooth. Then whisk in the cocoa powder. Whisk the melted chocolate mixture into the egg mixture until just combined.
5-Fold in the flour, espresso powder, and: Fold in the flour, espresso powder, and salt until just combined.
6-Pour half of the brownie batter into: Pour half of the brownie batter into the pan and spread it to the edges. (about 340 grams). Place the frozen cookie butter square on top of the batter, peeling the parchment paper off the top. Pour the rest of the batter on top and spread it evenly to the edges.
7-Break up the Biscoff cookies into pieces: Break up the Biscoff cookies into pieces and press them on top of the batter. Warm 2 tablespoons of cookie butter in the microwave for 15-20 seconds (until runny) and drizzle it over the top.
8-Bake the brownies in the preheated oven: Bake the brownies in the preheated oven for 30-40 minutes, or until a toothpick inserted into the center comes out covered in a few moist crumbs. Let the pan cool completely on a wire rack before removing. You can drizzle more cookie butter on top before cutting, then enjoy!
9-Store leftovers in an airtight container at: Store leftovers in an airtight container at room temperature for 2-3 days. They can be frozen after baking in an airtight container or freezer bag for up to 1 month.