Jerri Janz from Batter Up Cakes shows us how.
1 cup butter
2 cups sugar
3 cups all-purpose flour
1 cup milk
2 tbsp. baking powder
pinch of salt
8 egg whites
1 tsp. pure vanilla
Preheat oven to 325°F. Grease and lightly flour 3 9-inch round cake pans, shaking out excess flour. For ease of removal, cake pans may be lined on bottom with buttered wax or parchment paper. Cake pans should be filled about 2/3 full.
Cream butter thoroughly. Add sugar and beat until light and fluffy.
Sift together flour, baking powder, salt until combined well.
Stir together milk and vanilla.
Add alternately, in this order, 1/3 flour mixture, 1/2 milk mixture, 1/3 flour mixture, remaining milk, remaining flour mixture to the butter and sugar mixture.
In a clean bowl, beat the egg whites until stiff peaks form; the whites should be shiny and not dry in appearance.
Using a spatula, fold the whites into the batter gently, using a cutting motion, down through the center, across the bottom, up the sides, turning the bowl 1/4 turn with each fold and continuing until the egg whites are incorporated into the batter. It's OK for some puffs of egg white to still be visible; the goal is to keep as much air in the whites as possible. Don't overdo the folding in.
Bake the cake in a preheated 325°F oven for about 25 minutes, or until a toothpick inserted in center comes out clean. Cool on wire rack for 5 minutes before removing from pans.
Frost between layers with your favorite icing or filling.
1/4 c. butter, slightly softened
1/4 c. solid vegetable shortening
1 1/2 tsp. vanilla
5 c. confectioners' sugar (there are 4 c. in a lb.)
1/4 c. & 1 tbsp. milk
In a large mixing bowl: Cream butter and shortening with mixer. Add vanilla. Gradually add sugar, 1 cup at a time, beating well on medium speed. Scrape sides and bottom of bowl often. When all the sugar has been mixed in, icing will appear dry. Add milk and beat at high speed until light and fluffy. Keep icing covered with a damp cloth until you're ready to decorate. For best results, keep icing bowl in refrigerator when not using.