• Preheat the oven to 325°F. Grease and line two 8-inch cake pans with parchment paper.
• Sift the all-purpose flour and cornstarch together, then whisk in the baking powder and salt.
• Beat the butter and sugar in a large mixing bowl until light and fluffy, about 2-3 minutes.
• Add the eggs one at a time, mixing well after each. Stir in the vanilla extract.
• Alternate adding the dry ingredients and the milk, starting and ending with the dry ingredients. Stir in the sour cream until just combined.
• Divide the batter evenly between the prepared cake pans. Bake for 35-40 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. Wrap in plastic wrap and chill for 30 minutes before slicing.

Make the Simple Syrup

• Heat the water and sugar in a small saucepan over medium heat, stirring until the sugar dissolves. Remove from heat and stir in the vanilla extract. Let cool completely.

Make the Mascarpone Chantilly Cream

• Beat the mascarpone and cream cheese together until smooth. Add the powdered sugar and vanilla extract and mix until well combined.
• Slowly pour in the cold heavy cream while beating, and continue whipping until stiff peaks form. Chill until ready to use.

Assemble the Cake

• Use a serrated knife to slice each cake in half horizontally, creating four thin layers.
• Brush each layer lightly with simple syrup to keep them moist.
• Spread a thick layer of mascarpone Chantilly cream over the first cake layer, then sprinkle with an even layer of berries.
• Repeat with the remaining layers, finishing with cream on the top and sides.
• Pipe extra cream around the edges and decorate the top with fresh berries. ( I used tip 1M from this set. )
• Chill the cake for at least 1 hour before slicing to help the layers set.