Add candy bars to the bowl of a blender/food processor until they are pea size crumbs. Divide into 2 bowls, one for frosting and one for garnishing. Set aside.
Combine butter, peanut butter, powdered sugar, vanilla and salt in the bowl of a stand mixer fitted with a paddle attachment. Beat on medium speed until smooth and creamy, about 3 minutes, then add the candy bar crumbs reserved for the frosting (continue to hold back the crumbs used for garnish). Add them in on low, then switch to medium speed and beat until light and creamy. If mixture is too thick, add milk 1 tablespoon at a time beating between each addition until it is thick like frosting, but thin enough to spread with a spatula. Beat mixture until well combined.
Spread frosting over top of cooled cupcakes, 9x13 cake or 9-inch (2-layer) cake, brownies or your favorite dessert. Sprinkle reserved candy bar crumbs over the top of the frosting to garnish. Serve and enjoy.