Preheat your oven to 350°F (175°C) and prepare two 9-inch round cake pans.
In a large mixing bowl, whisk together the flour, baking powder, and salt.
In another bowl, cream together the softened butter and sugar until light and fluffy.
Add the eggs one at a time, mixing until well combined after each addition, then stir in the vanilla extract.
Gradually add the dry ingredients to the butter mixture, alternating with the milk, beginning and ending with flour.
Divide the batter evenly between the prepared pans and smooth the tops.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cakes to cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely.
Once cooled, whip the cream to soft peaks and gently fold in 1 tablespoon of sugar, if desired.
Place one cake layer on a serving platter and spread a generous amount of whipped cream over the top, followed by a layer of mixed berries.
Carefully add the second layer of cake and repeat the process of layering with whipped cream and berries on top.
Finish with a final dollop of whipped cream and a scattering of remaining berries on top for garnish.
Chill the cake in the refrigerator for at least an hour before serving to allow the flavors to meld.