1/2 cup butter
1 1/2 cups white sugar
4 egg whites
9 tablespoons milk
2 3/4 cups chopped pecans
1 1/4 teaspoons vanilla extract
1/2 cup confectioners' sugar
3 cups rolled oats
Preheat oven to 350 degrees F (175 degrees C). Grease and flour two 8-inch round cake pans. Lightly grease and flour a 9x13-inch pan.
In a large bowl, cream together the butter, sugar, egg whites and milk. Beat in the flour mixture alternately with the milk. Stir to blend well. Pour batter into prepared pans.
Bake in the preheated oven for 25 to 29 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow to cool completely. Once cool, frost with confectioners' sugar but do not sprinkle with confectioners' sugar or oats. Cool cake completely before frosting.
Distribute peanut butter frosting by spoonfuls onto cooled cake layers. Serve immediately. To make the frosting: Beat together the cocoa and powdered brown sugar. Powder, butter and peanut butter mixture and pour over peanut butter cake layers. Chill before use.