Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a large bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.

Add the milk, vegetable oil, eggs, and vanilla extract to the dry ingredients. Mix until well combined.

Stir in the boiling water until the batter is smooth. Divide the batter evenly between the prepared pans.

Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean. Let cool in pans for 10 minutes, then turn out onto wire racks to cool completely.

In a small bowl, combine the coffee and coffee liqueur. Set aside.

In a medium bowl, beat the mascarpone cheese, powdered sugar, and 1 tablespoon of the coffee mixture until smooth.

In a separate bowl, whip the heavy cream until stiff peaks form. Gently fold the whipped cream into the mascarpone mixture.

To assemble the cake, place one layer on a serving platter. Brush with half of the remaining coffee mixture.

Spread half of the mascarpone mixture over the cake layer. Top with the second cake layer and repeat with the coffee mixture and mascarpone topping.

Dust the top of the cake with cocoa powder before serving.