Prepare the Brownies:

Preheat the oven to 350°F (175°C). Line a 9×9-inch square baking pan with parchment paper, leaving an overhang on the sides for easy removal.

In a medium bowl, combine the chopped chocolate and cocoa powder. Set aside.

In a small pan, melt the butter over medium heat. Once melted, continue cooking until the milk solids turn golden and the mixture smells nutty. Remove from heat and pour over the chocolate and cocoa powder. Stir until the chocolate melts and the mixture is smooth. Set aside.

In a large mixing bowl, whisk the eggs, granulated sugar, and brown sugar until well combined. Slowly add the brown butter-chocolate mixture while whisking constantly until incorporated.

Fold in the flour until just combined, being careful not to overmix.

Pour the brownie batter into the prepared pan and spread it evenly. Bake for 28-30 minutes, or until a toothpick comes out with a few wet crumbs. Let cool.

Prepare the Mascarpone Cream:

In a mixing bowl, beat the mascarpone cheese with an electric hand mixer until smooth. Add the whipping cream, powdered sugar, and vanilla extract, then beat until the mixture thickens to a spreadable consistency (about 5-10 minutes). Set aside.

Prepare the Ladyfinger Soak:

In a shallow bowl or tall cup, stir together espresso powder, hot water, and coffee liqueur (if using).

Quickly dip each ladyfinger into the espresso soak for about 1 second on each side. Arrange them on top of the cooled brownie layer, making sure not to soak them too long.

Assemble the Tiramisu Brownies:

Spread the mascarpone cream evenly over the layer of ladyfingers, smoothing with an offset spatula.

Chill and Serve:

Chill the assembled brownies in the fridge for about 1 hour to allow the cream to set and the ladyfingers to soften.

Dust the top with cocoa powder using a fine mesh sieve.

Lift the brownies out of the pan using the parchment paper overhang, then slice into squares, wiping the knife between each cut for clean edges.