Cook butter in a small heavy saucepan over medium heat, stirring constantly, 6 to 8 minutes or until butter begins to turn golden brown. Remove pan from heat immediately, and pour butter into a small bowl. Cover and chill 1 hour or until butter is cool and begins to solidify.
Beat butter at medium speed with an electric mixer until fluffy; gradually add powdered sugar alternately with milk, beginning and ending with powdered sugar. Beat mixture at low speed until well blended after each addition. Stir in vanilla.
Cupcakes With Browned Butter Frosting: Prepare 1 (16-oz.) package pound cake mix according to package directions. Place 24 paper baking cups in muffin pans; spoon batter evenly into paper cups, filling two-thirds full. Bake at 350° for 20 minutes or until a wooden pick inserted in center of cupcake comes out clean. Remove cupcakes from pans, and let cool completely on wire racks. Spread cupcakes evenly with Browned Butter Frosting; garnish with fresh mint leaves and edible violas, if desired. Makes 24 cupcakes. Prep: 15 min., Bake: 20 min.