Prepare the Cake Pans and Oven

Preheat your oven to 350°F (175°C). Grease and flour two 8- or 9-inch round cake pans, or line them with parchment paper for easy removal.

Make the Cake Batter

In a medium bowl, whisk together the flour, baking powder, and salt. In a large bowl, beat the butter and sugar together until light and fluffy, about 2-3 minutes. Add the eggs one at a time, beating well after each addition, then add the vanilla extract.

Combine Ingredients

Gradually add the flour mixture to the butter mixture, alternating with the milk. Begin and end with the flour mixture, mixing just until combined to avoid overworking the batter.

Bake the Cakes

Divide the batter evenly between the prepared pans. Bake for 20-25 minutes, or until a toothpick inserted in the center comes out clean. Let the cakes cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely.

Prepare the Chantilly Frosting

In a large bowl, beat the mascarpone cheese, powdered sugar, and vanilla extract until smooth and creamy. Gradually add the heavy whipping cream and continue to beat until stiff peaks form. Be careful not to overwhip, as the frosting should be light and fluffy.

Assemble the Cake

Place one layer of cake on a cake stand or serving plate. Spread a layer of Chantilly frosting over the cake, then sprinkle with mixed berries. Place the second cake layer on top and spread the remaining frosting evenly over the top and sides of the cake.

Garnish and Serve

Decorate the top of the cake with extra berries and mint leaves if desired. Chill the cake for at least 1 hour before serving to set the frosting and flavors.