Heat oven to 350 F. Grease and flour 2 8 or 9-inch round cake pans. In a large bowl, blend cake mix, vanilla pudding, 1/2 cup peanut butter, milk and eggs until moistened. Beat 2 minutes at highest speed. Fold in 1/2 cup of chopped peanuts. Bake at 350 F. for 35 to 45 minutes or until toothpick inserted in the center comes out clean. Cool cake in pans 5 minutes and remove to racks to cool. Blend the frosting with 1/4 cup of peanut butter. Frost the cake and sprinkle with the remaining chopped peanuts.