• Preheat oven to 350°F. Grease three 8 or 9" cake pans, line with parchment paper, and grease the parchment paper, too.
• In a medium bowl, whisk the sifted flour, baking powder, baking soda, and salt. Set aside.
• In a large bowl, beat the softened butter and sugar until smooth and creamy. Add eggs, 1 at a time, and mix until just combined after each. Add vanilla extract and sour cream and mix until smooth, scraping down the sides of the bowl as needed.
• Add dry ingredients to wet ingredients in 3 additions and mix until just combined after each. Add the milk and mix until smooth. Do not overmix.
• Divide the batter evenly into the prepared cake pans. Bake for 22-24 minutes until a toothpick inserted into the center comes out clean. If your cakes are baking unevenly, rearrange them in the oven midway through baking.
• Allow the cakes to cool slightly in the pan and then cool completely in the fridge before topping.

Whipped Cream Topping:

• Make the whipped cream in advance and keep it cool in the fridge. This will allow time for the cream to harden and will make topping the cakes easier.
• In a large bowl, beat heavy cream, powdered sugar, and vanilla extract until stiff peaks form. About 5 minutes. Cool the whipped cream in the fridge for 1 hour to harden.
• Once the cakes have cooled completely, begin assembling the layers. If the cakes are dome-shaped, use a large serrated knife to level off the top. Start with one cake layer and spread whipped cream on top. Arrange sliced berries on top. Top with a second cake layer. Add more cream and fresh berries and top with the final cake layer. Top with more whipped cream and fresh berries. Spread a small layer of cream around the sides of the cake, if desired.
• Cool the assembled cake for at least 30 minutes in the fridge before slicing and serving.
• Cover leftover cake and keep in the fridge for up to 5 days.