Ingredients
½ teaspoon (2 mL) vanilla extract
1 teaspoon (5 mL) coffee liqueur
1 teaspoon instant coffee powder
3 teaspoons cocoa powder, divided
1-1/4 cups (133 g) powdered sugar, divided
1 tub (16 ounces) (453 g) mascarpone cheese
1 cup (250 mL) heavy cream
4 eggs
1/4 teaspoon kosher salt
1 cup (120 g) all-purpose flour
½ cup (113 g) unsalted butter
1 cup (250 mL) water
Step by step
Preheat oven to 400°F. Line baking sheet with parchment paper.
To prepare cake, heat water and butter in small saucepan until butter is melted. Transfer to Bowl of KitchenAid® Artisan Stand Mixer. Attach Bowl and Flat Beater to Mixer. Turn to Speed 2 and gradually add flour and salt. Mix 1 minute or until combined. With machine running on Speed 2, add eggs, one at a time, mixing until well blended.
Spoon dough into large piping bag fitted with ¼-inch plain tip. Pipe long vertical strips of dough onto prepared pan about 1/8 to 1/4 inch apart. Bake 20 minutes. Cool completely.
To prepare mousse, add cream to clean Bowl of KitchenAid® Artisan Stand Mixer. Attach Bowl and Wire Whip to Mixer. Turn to Stir and gradually add ½ cup powdered sugar. Turn to Speed 8 and whip until stiff peaks form. Transfer to separate bowl.
Add mascarpone cheese, ½ cup powdered sugar, 2 teaspoons cocoa, instant coffee, liqueur and vanilla to Mixer Bowl. Attach Bowl and Flat Beater to Mixer. Turn to Stir and mix 1 minute or until well blended. Turn to Speed 4 and beat until light and fluffy. Gently fold whipped cream into mascarpone mixture with rubber spatula.
Cut cake layer lengthwise into two squares using serrated knife. Spread mousse evenly onto one layer. Gently top with second cake layer.
Mix remaining ¼ cup powdered sugar and 1 teaspoon cocoa powder. Sprinkle over cake to garnish.