3/4 cup Biscoff cookie butter, plus extra for topping
1/2 cup light or dark brown sugar, packed
1/2 cup granulated sugar
2 large eggs
1 large egg yolk
1 tablespoon vanilla extract
10 tablespoons unsalted butter
2/3 cup + 1/4 cup semi-sweet chocolate chips
1/4 cup unsweetened Dutch cocoa powder
2/3 cup + 1 tablespoon all-purpose flour
1 teaspoon espresso powder
1/2 teaspoon fine sea salt
4–5 Biscoff cookies, for the top
Instructions
Preheat oven to 350°F (175°C). Line an 8×8-inch or 9×13-inch baking pan with parchment paper, leaving an overhang, then lightly grease.
Melt the semi-sweet chocolate chips (2/3 cup + 1/4 cup) using a double boiler or microwave until smooth. Set aside to cool slightly.
In a large bowl, beat softened unsalted butter (10 tbsp) with granulated sugar (1/2 cup) and light brown sugar (1/2 cup) until light and fluffy (2-3 minutes).
Beat in 2 large eggs one at a time, then the 1 large egg yolk, mixing well after each. Stir in 1 tablespoon vanilla extract. Beat for another 1-2 minutes until glossy.
Gently fold the slightly cooled melted chocolate into the egg-butter-sugar mixture until just combined.
In a separate bowl, whisk together 1/4 cup unsweetened Dutch cocoa powder, 2/3 cup + 1 tablespoon all-purpose flour, 1 teaspoon espresso powder, and 1/2 teaspoon fine sea salt.
Gradually add dry ingredients to wet, mixing on low speed or by hand until just combined. Do not overmix. If using additional chocolate chips in the base, fold them in now.
Warm the 3/4 cup Biscoff cookie butter slightly. Pour about two-thirds of the brownie batter into the prepared pan. Dollop roughly half of the warmed 3/4 cup Biscoff over this layer. Carefully spoon the remaining one-third of brownie batter over. Drizzle the remaining portion of the 3/4 cup Biscoff, along with any ‘extra cookie butter’ for topping, generously over the top. Use a knife or skewer to gently swirl.
Crush the 4-5 Biscoff cookies and sprinkle them evenly over the swirled top of the batter.
Bake for 30-35 minutes (for 8×8 pan) or 25-30 minutes (for 9×13 pan), until edges are set, center has a slight wobble, and a toothpick inserted comes out with moist crumbs.
Cool completely in the pan on a wire rack for at least 2-3 hours (or overnight/in fridge for best results). Lift out using parchment overhangs, slice with a sharp, warm knife, and serve. Store leftovers in an airtight container at room temperature.