**Preheat the Oven**: Preheat to 350°F. Spray three 6-inch cake pans with non-stick spray and line the bottoms with parchment paper.

**Mix Dry Ingredients**: In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.

**Cream Butter and Sugar**: In a large mixing bowl, beat butter and sugar on high speed until fluffy (3-4 minutes).

**Add Eggs and Vanilla**: Add eggs and vanilla, mixing on medium-high speed until smooth and slightly fluffy (2-3 minutes). Scrape the bowl as needed.

**Combine Wet and Dry**: Alternate adding the flour mixture and buttermilk to the butter mixture, mixing on low speed until just combined. Scrape the bowl as necessary.

**Bake**: Divide the batter evenly among the pans. Bake for 29-32 minutes, or until a toothpick comes out clean. Let cakes cool in pans for 5 minutes, then transfer to a wire rack to cool completely.

**Whip Cream Cheese**: In a large bowl, whip cream cheese on high speed until smooth (1-2 minutes).

**Add Mascarpone and Sugar**: Add mascarpone and sift in powdered sugar, mixing on medium-low speed until combined (1 minute).

**Whip Cream**: In a separate bowl, whip heavy cream on high speed until stiff peaks form.

**Combine**: Fold the whipped cream into the mascarpone/cream cheese mixture until well combined.

**Layer and Fill**: Place the first cake layer on a turntable. Spread a layer of Chantilly cream on top, then pipe a border of frosting around the edge. Add a third of the fresh berries. Repeat with the next layer.

**Frost the Cake**: Place the final layer on top. Spread dollops of frosting on the sides and top of the cake. Smooth out with a spatula and scraper to achieve a semi-naked look.

**Decorate**: Top with more fresh berries. Serve and enjoy!

This Chantilly cake is sure to be a hit at any summer gathering. Enjoy every delicious, berry-filled bite!