Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking pan or line it with parchment paper.

Melt 1 cup of dark chocolate and 1/2 cup of unsalted butter in a medium saucepan over low heat, stirring frequently until smooth.

Stir in 1 cup of granulated sugar, then add 3 large eggs one at a time, mixing well after each addition.

In a separate bowl, whisk together 1 cup of all-purpose flour and 2 tablespoons of espresso powder. Gradually add to the chocolate mixture.

Pour the brownie batter into the prepared pan and bake for about 30 minutes or until the edges are set but center is still slightly soft.

While cooling, prepare the mascarpone layer by mixing 1 cup of mascarpone cheese, 1/4 cup of sugar, and 2 tablespoons of coffee liqueur until smooth.

Spread the mascarpone mixture over the cooled brownies and chill in the fridge for at least 2 hours.

To serve, use a sharp knife dipped in hot water to slice into squares, wiping the knife between cuts.