- Preheat oven to 350°F. Grease and line three 9-inch cake pans. 
- Mix flour, baking powder, and salt. 
- Cream butter and sugar until fluffy (5 minutes). Add eggs one at a time, then vanilla. 
- Alternate adding dry ingredients and milk to butter mixture. 
- Divide batter between pans. Bake 25-30 minutes. 
- Cool completely. 
- Whip cream to soft peaks. Mix mascarpone, powdered sugar, vanilla, and salt separately. Fold together. 
- Macerate berries with sugar and lemon juice for 15 minutes. 
- Layer cake: cake, cream, berries. Repeat. 
- Frost exterior with remaining cream. 
- Garnish with fresh berries and mint.