Preheat oven to 375 degrees. Butter a 13″ x 9″ baking dish, set aside. In a mixing bowl combine flour, baking powder and salt, set aside. In the bowl of an electric mixer, whip together butter and sugar until pale and fluffy about 3-4 minutes. Stir in egg and egg white. Add sour cream and vanilla and mix until blended. Slowly add dry mixture and stir until well combine. With buttered hands, gently press (so gently almost patting) mixture into buttered baking dish. Bake 17 – 20 minutes until toothpick inserted into the center comes out clean and edges are lightly golden. Cool completely, then frost and cut into squares.
1/4 cup unsalted butter, softened
2 cups powdered sugar
2-3 Tbsp half and half
1/2 tsp vanilla
Pinch of salt
Several drop food coloring (optional)
In a mixing bowl, with an electric mixer, whip together butter and powdered sugar and half and half until fluffy. Stir in vanilla and salt. Add in food optional food coloring and mix until well blended.