For the cake: Cream butter, sugar and egg until light and fluffy. Sift dry ingredients together. Slowly alternate adding buttermilk and dry ingredients to the butter mixture. Until completely mixed. Line baking sheet with parchment paper. Use ¼ cup or medium ice cream scoop to dispense batter, 2 inches apart.
Bake in preheated 350°F oven for 15-16 minutes.
For the Filling: Cream all ingredients together until light and fluffy. Spread between to cakes.