Preheat the oven to 350°F (175°C). Grease and flour a 9×9-inch metal baking pan or line it with parchment paper for easy removal.

Whisk the flour, cocoa powder, and salt together in a medium bowl. Set aside.

Place the semisweet chocolate and butter in a heatproof bowl over a saucepan of gently simmering water. Stir until completely melted and smooth.

Whisk the granulated sugar and brown sugar into the melted chocolate mixture until thoroughly combined.

Remove the chocolate mixture from the heat and allow it to cool to room temperature.

Once cooled, whisk in the eggs one at a time. Stir in the vanilla extract.

Add the dry ingredients and gently whisk or fold just until no visible streaks of flour remain. Avoid overmixing.

Spread the brownie batter evenly in the prepared baking pan.

Bake for 20–30 minutes. The brownies are ready when a toothpick inserted near the center comes out with a few moist, fudgy crumbs rather than wet batter.

Allow the brownies to cool completely to room temperature before adding the topping.

For the topping, combine the heavy cream and instant espresso powder in a mixing bowl. Stir until the espresso powder has dissolved.

Add the mascarpone, powdered sugar, and vanilla. Beat on medium speed until the mixture becomes smooth, light, and fluffy.

Spread the espresso mascarpone cream evenly over the cooled Tiramisu Brownies.

Place the remaining cocoa powder in a fine-mesh sieve and lightly dust it over the mascarpone layer.

Refrigerate for at least 1 hour to allow the topping to firm up before slicing and serving.