Bake the Brownies: Whisk butter and sugar, add eggs and vanilla, then fold in dry ingredients. Bake at 350°F (175°C) for 20–25 minutes. Cool completely.
Add Coffee Layer: Quickly dip ladyfingers in cooled espresso and arrange in a single layer over the brownies.
Make the Crema: Whip heavy cream, powdered sugar, and vanilla to stiff peaks, then gently fold in the mascarpone until smooth.
Assemble & Chill: Spread the crema evenly over the ladyfingers. Chill for at least 2 hours.
Serve: Dust generously with cocoa powder, slice, and enjoy!
