Start by preparing the brownie base. Melt the dark chocolate and butter together until smooth and glossy, either over a pot of simmering water or in the microwave for 30-second intervals, stirring each time. 

Let it cool for a bit so it doesn’t cook the eggs. While the chocolate mixture cools, whisk together your eggs, granulated sugar, and brown sugar until fluffy. 

Stir the cooled chocolate-butter mixture into the eggs and sugar until combined.

Next, sift in the cocoa powder and flour, making sure there are no lumps.

Gently fold everything together until fully combined, be careful not to overmix to avoid dense brownies. 

Pour the batter into a greased 9x9-inch pan (line with parchment paper for easy cleanup) and bake at 350°F for 25-30 minutes, or until a toothpick comes out with a few moist crumbs. 

Let the brownies cool completely in the pan to make assembly easier.

While the brownies cool, prepare the mascarpone cream. 

Beat the cold mascarpone cheese and whipping cream together until soft peaks form. 

Add powdered sugar and vanilla extract and continue beating until smooth and fluffy. This creamy texture will layer beautifully on top of the brownies.

Now, make the ladyfinger soak. In a shallow dish, dissolve espresso powder in hot water until smooth. If you're using coffee liqueur or rum, add it now. 

Dip each ladyfinger into the coffee mixture quickly, don’t let them get too soggy, just enough to absorb the flavor.

Once the brownies are fully cooled, layer the dipped ladyfingers over the brownies.

Spread the mascarpone cream evenly over the ladyfingers, smoothing it out to cover everything.

Refrigerate the brownies for at least an hour to let the flavors come together and the cream set. 

When ready to serve, dust the top with cocoa powder and slice into delicious, indulgent servings. Enjoy!