Preheat the oven to 350°F (175°C). Line a baking pan with parchment paper, leaving enough overhang to make removing the brownies easier.

Place the butter and bittersweet chocolate chips in a heatproof bowl. Melt them together over a bain-marie, stirring until completely smooth. Set aside to cool slightly.

In a separate large mixing bowl, whisk the eggs, granulated sugar, brown sugar, alcohol-free vanilla, and salt until smooth and well combined.

Slowly pour the cooled chocolate and butter mixture into the egg mixture while stirring.

Sift the all-purpose flour and cocoa powder over the wet ingredients.

Gently fold everything together just until no dry streaks remain. Avoid overmixing.

Transfer the brownie batter to the prepared baking pan and spread it into an even layer.

Bake for approximately 30 minutes, or until a toothpick inserted near the center comes out with several moist crumbs rather than wet batter.

Place the pan on a wire rack and allow the brownies to cool completely before adding the topping.

To prepare the mascarpone cream, place the mascarpone, heavy cream, sugar, salt, alcohol-free vanilla, and instant coffee powder in a mixing bowl.

Beat with a hand mixer or stand mixer until the mixture becomes smooth, light, and fluffy. Avoid excessive whipping.

Once the brownie layer is completely cool, spread the mascarpone coffee cream evenly over the surface.

Refrigerate the assembled Tiramisu Brownies for at least 2 hours. For the best set and developed flavor, chill overnight.

Just before serving, generously dust the mascarpone layer with unsweetened cocoa powder.

Lift the brownies from the pan using the parchment paper and slice into squares with a clean, sharp knife.