Prepare the Cake Layers

Preheat your oven to 350°F (175°C). Grease two 8-inch round cake pans and line the bottoms with parchment paper. In a medium bowl, whisk together flour, baking powder, and salt. Set aside.

Make the Sponge Cake

In a large bowl, beat the eggs and sugar with an electric mixer on high speed until thick and pale, about 5 minutes. Add the vanilla extract and mix. Gently fold in the flour mixture until just combined, being careful not to overmix. Divide the batter evenly between the two prepared pans.

Bake the Cakes

Bake for 20-25 minutes or until a toothpick inserted into the center comes out clean. Let the cakes cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely.

Prepare the Coffee Soak

In a small bowl, combine the cooled espresso and coffee liqueur (if using). Set aside.

Make the Mascarpone Filling

In a large mixing bowl, beat the heavy cream until stiff peaks form. In another bowl, mix the mascarpone cheese, powdered sugar, and vanilla extract until smooth. Gently fold the whipped cream into the mascarpone mixture until well combined and fluffy.

Assemble the Cake

Slice each cake layer in half horizontally to create four thin layers. Place one layer on a serving plate and brush generously with the coffee soak. Spread a layer of mascarpone filling on top. Repeat with the remaining layers, brushing each with coffee and spreading with filling, ending with a layer of mascarpone on top.

Decorate

Dust the top of the cake generously with cocoa powder using a fine mesh sieve. For an elegant touch, add chocolate shavings or curls.

Chill Before Serving

Refrigerate the assembled cake for at least 2 hours to allow the flavors to meld and the filling to set.