Combine cake mix, eggs, bananas, oil, sugar, milk and vanilla.
Beat at low speed for 30 seconds. Beat at medium speed for 2 minutes.
Stir in 1/2 cup chopped nuts.
Bake at 350 degrees in 2-9 inch greased and floured layer pans for 33-38 minutes.
While cake is baking, place 1 cup chopped nuts and butter in skillet. Cook on medium heat, stirring until nuts are toasted. Stir into frosting. Cool. Frost cake.
Not a NESTLÉ®-tested recipe.