Preheat Oven:
Preheat to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper and lightly grease.
Make the Brownie Batter:
Melt butter in a small pot or microwave-safe bowl. Stir in sugar, eggs, and vanilla extract until combined. Add cocoa powder, flour, baking powder, and salt. Stir until smooth.
Bake:
Pour the brownie batter into the pan. Bake for 22–25 minutes, or until a toothpick comes out with moist crumbs. Allow to cool completely.
Make the Tiramisu Cream:
In a large bowl, beat mascarpone cheese, espresso powder, powdered sugar, and coffee liqueur until smooth. In another bowl, whip heavy cream until stiff peaks form. Fold the whipped cream into the mascarpone mixture gently.
Assemble:
Spread tiramisu cream evenly over cooled brownies. Smooth with a spatula and dust with cocoa powder.
Chill & Serve:
Refrigerate for at least 1 hour before slicing. Serve chilled for the best texture and flavor.