Make Sponge Cake: Preheat oven to 350°F (175°C). Line two 10 inch round cake pans with parchment paper and spray with nonstick spray.

In a stand mixer with whisk attachment, beat eggs on high until foamy (about 4 minutes). Slowly add 1 cup sugar and vanilla; continue beating until mixture is very thick, pale, and tripled in volume (another 4-5 minutes).

Sift flour, cornstarch, and baking powder over the egg mixture. Gently fold in with a whisk until just combined. Do not overmix.

Divide batter evenly between prepared pans. Bake for 28-30 minutes, until a toothpick comes out clean. Cool in pans for 10 minutes, then transfer to a wire rack to cool completely.

Make Cream Filling: In a stand mixer with paddle attachment, beat cream cheese, mascarpone, 2 ½ cups powdered sugar, and ¼ cup Kahlua until smooth. If mascarpone is runny, refrigerate mixture for 40 minutes.

In a separate bowl, beat egg product with an electric hand mixer until thick and creamy (5-7 minutes). Gently fold whipped egg product into the cream cheese mixture until just incorporated. Set aside.

Make Coffee Soak: In a small bowl, stir together espresso, 3 tablespoons Kahlua, and 1 tablespoon sugar until dissolved.

Assemble Cake: Slice each cooled cake layer in half horizontally to make 4 thin layers. Place one layer on a serving plate. Gently soak with coffee mixture using a soaker bottle or pastry brush.

Spread about 1 ¼ cups of cream over the soaked layer. Dust lightly with cocoa powder. Repeat layers with remaining cake, soak, cream, and cocoa, ending with a cream layer on top.

Use remaining cream to frost the sides if desired. Dust the top generously with cocoa powder.

Chill: Cover loosely and refrigerate for at least 6 hours, preferably overnight, to allow flavors to meld. Serve cold.