Preheat oven to 350°F.
Sift together flour, baking powder, and salt; set aside. Cream shortening with sugar and vanilla until light and fluffy. Add eggs yolks, 1 at a time, beating well after each addition. Add flour mixture and milk alternately, beating well after each addition.
Ensure that mixing bowl and beaters have no oil residue, then beat egg whites until stiff but not dry and fold gently into cake batter.
Grease and flour 3 9-inch cake pans. Divide batter evenly among pans, transfer to oven, and bake for 30 minutes or until cake springs back when lightly touched. Remove and, when pans are cool enough to handle, gently remove cakes, place on a wire rack, and cool completely.
Place the first layer on a serving platter; generously frost top. Add second layer and frost; top with final layer and spread frosting over top and sides; garnish with chopped pecans (optional).

Icing on the Cake: Chocolate Buttercream

Sift confectioner’s sugar; place into mixing bowl and whisk in cocoa powder. Cream together with butter and vanilla. Add ½ cup milk, then, 1 tablespoon at a time, add remaining milk until frosting reaches spreading consistency.
Makes about 2 cups.