In medium saucepan, cook butter over medium-low heat until brown and fragrant, about 10-15 minutes. Remove from pan and cool until butter is room temperature and thickened, but still soft.
Preheat oven to 350ºF. Prepare muffin pans with baking cups.
In large bowl, stir together flour, baking powder, baking soda and salt.
In large bowl, beat 1/2 cup browned butter, granulated sugar and brown sugar with electric mixer until smooth and creamy. Add eggs, one at a time, mixing well after each. Add Juicy Peach and Creamy Vanilla Custard Flavors and beat well. Alternately add dry ingredients with sour cream and milk, scraping bottom and sides of bowl often. Divide batter evenly into baking cups, about 2/3 full.
Bake 18-20 minutes or until toothpick inserted in center of cupcake comes out clean. Cool cupcakes in pan on cooling grid 5 minutes. Remove from pan; cool completely on grid.
For icing, beat remaining browned butter and shortening with electric mixer until creamy. Add Juicy Peach and Creamy Vanilla Custard Flavors and beat well. Gradually add confectioners? sugar, one cup at a time; beating well on medium speed. Scrape sides and bottom of bowl often. Gradually add milk and beat at medium speed until light and fluffy.