Preheat your oven to 350°F (177°C) and prepare two 6-inch round cake pans by greasing and lining them with parchment paper.

In a mixing bowl, sift together the cake flour, baking powder, and salt. Set aside.

In a separate cup, dissolve the instant espresso powder in boiling water and let it cool.

Beat the softened butter until creamy, then gradually add sugar and beat until fluffy. Scrape down the bowl as needed.

Add vanilla extract and incorporate the eggs one at a time, mixing well. Alternate adding the dry ingredients and the milk, mixing until just combined, then fold in the cooled espresso.

Divide the batter into the prepared pans and bake for 20-25 minutes until a toothpick comes out clean. Allow to cool slightly in the pans.

Cool cake layers in the pans for 5 minutes then transfer to wire racks to cool completely.

Whip the mascarpone cheese until creamy, mix in powdered sugar and coffee until smooth, then fold in heavy whipping cream.

Slice each cooled layer in half to create four layers. Soak each layer with coffee or liquor, then spread frosting between layers and on the top and sides of the cake. Dust with cocoa powder.