Preheat your oven to 350°F (175°C). Grease and line three 8-inch round cake pans with parchment paper.

In a large mixing bowl, whisk together the cake flour, baking powder, and salt until well combined.

In a separate bowl, beat the unsalted butter and granulated sugar together until light and fluffy, about 3-5 minutes. Add eggs one at a time, followed by vanilla extract.

Gradually alternate adding the dry mixture and whole milk to the creamed mixture, mixing until just combined.

Divide the batter evenly among the prepared pans and smooth tops with a spatula. Bake for 25-30 minutes or until a toothpick comes out clean.

Let cakes cool in pans for about 10 minutes before transferring to a wire rack.

Combine mixed berries, sugar, and a squeeze of lemon juice in a medium saucepan over medium heat. Stir until berries break down, about 5-7 minutes.

Stir in a cornstarch slurry and cook for an additional 2-3 minutes until thickened. Let cool completely.

Beat cold heavy cream and cream cheese until soft peaks form. Gradually add sifted powdered sugar and vanilla extract until well incorporated.

Once cooled, place one layer of cake on a serving plate. Spread chantilly cream followed by berry filling. Repeat with second layer and finish with last layer.

Apply a thin crumb coat and chill in the refrigerator for 30 minutes. Then apply a thicker layer of frosting and decorate with fresh berries.