Cake – 2 3/4 cups all-purpose flour – 1/2 teaspoon salt – 2 teaspoons baking powder – 1/2 teaspoon baking soda – 1 cup European butter at room temperature – 2 cups granulated sugar – 4 large eggs at room temperature – 1 teaspoon vanilla extract – 1/4 cup whole milk – 1 scant cup sour cream Blueberry sauce – 1/4 cup water – 3 tablespoons sugar – 2 tablespoons lemon juice – 3/4 cup frozen blueberrie Filling – 2 cups heavy cream – 1/4 cup powdered sugar – 1 teaspoon vanilla bean paste –1/2 cup mascarpone cheese – ▢1/2 tablespoons lemon zest – 14 oz frozen wild blueberries thawed Frosting – 2.5 oz white chocolate – 1 cup heavy cream – 2 oz frozen wild blueberries thawed – 1/2 cup fresh blueberries optional