Preheat the oven to 350°F (175°C). Grease and flour two 8-inch round cake pans.

In a bowl, whisk together flour, baking powder, and salt.

In another large bowl, cream the butter and sugar until light and fluffy.

Add eggs one at a time, beating well after each. Stir in vanilla.

Alternately add the dry ingredients and milk to the butter mixture, beginning and ending with the flour. Mix just until combined.

Stir in the cooled espresso or coffee.

Divide the batter evenly between the prepared pans.

Bake for 25–30 minutes or until a toothpick comes out clean. Let cool in the pans for 10 minutes, then transfer to a wire rack.

Make the syrup: Combine coffee, sugar, and coffee liqueur in a small saucepan. Warm until sugar dissolves, then cool.

Make the frosting: Beat the heavy cream until soft peaks form. In another bowl, beat mascarpone, powdered sugar, and vanilla until smooth. Fold in the whipped cream until fully combined and fluffy.

Once cakes are cool, brush them with the coffee syrup generously.

Spread half the mascarpone frosting over the bottom layer, then top with the second cake layer and frost the top and sides.

Dust with cocoa powder and sprinkle chocolate shavings if desired.

Chill the cake for at least 2 hours before serving.