Preheat your oven to 350° F. Spray a 9×9 ceramic or metal pan with nonstick spray and line with parchment paper.

Melt the butter and both chocolates in a microwave-safe large bowl in 30-second intervals, stirring between each, until fully melted and smooth. Whisk in the sugars until combined.

Add the eggs and vanilla, and whisk until combined, then continue whisking for 2 minutes.

Add the flour, salt, cocoa, and espresso powder, and fold in with a rubber spatula until the last streaks of flour just disappear into the batter. Fold in 1 cup of the crushed biscoff cookies.

Spread half the batter evenly in your prepared pan, and dollop ⅓ cup of cookie butter on top. Swirl it in with a butter knife.

Dollop on the remaining brownie batter and evenly spread it out. Add the remaining biscoff cookie pieces, and dollop on the remaining cookie butter, swirling it in.

Bake for 35-43 minutes. A toothpick inserted into the center should pull out moist crumbs, not wet batter, and should come out clean at the edges.

Let the brownies rest for about 30-40 minutes before digging in or let cool completely before slicing and serving. Store cooled brownies in an airtight container at room temp for 3-4 days or in the fridge for 5-6.