Preheat your oven to 180°C (356°F). Prepare your 7-inch square brownie pan by brushing it with unsalted butter and lining it with parchment paper.

In a heatproof bowl over simmering water, combine the semi-sweet chocolate and butter. Stir until melted and smooth.

In a separate bowl, whip together the eggs, granulated sugar, and brown sugar until pale and fluffy, about 5 to 7 minutes.

Pour the chocolate and butter mixture into the whipped egg mixture. Gently fold until just combined.

Sift in the flour, cocoa powder, cinnamon, and salt. Gently fold into the batter.

Pour half of the batter into the prepared pan, drizzle with half of the Biscoff spread, then layer the remaining batter and drizzle with more Biscoff.

Bake for 25-30 minutes, until the edges look set and the center is slightly gooey.

Allow the brownies to cool in the pan for at least 2 hours before slicing.