Lightly grease 2 9-inch round cake pans. Prepare cake mix according to package directions. Blend in 1/2 cup peanut butter. Pour batter into cake pans. Bake according to package directions. Cool. For frosting: In a mixing bowl, whip cream cheese until light and fluffy. Beat in honey, confectioner's sugar, vanilla extract, and nutmeg. Blend in peanut butter and milk. Stir in ground peanuts. Spread about 1 cup frosting between cake layers. Frost top and sides of cake with remaining frosting. Optional: top each serving with banana slices.