These Cupcakes will make you swoon! Moist and Fluffy Vanilla Cake with a Tagalong baked right in, topped with Peanut Butter Cookie Buttercream Frosting and dipped in Chocolate. You'll be in Girl Scout Cookie Heaven!
Place the egg whites and sugar in a mixing bowl, and set over a pot of simmering water.
Cook, whisking continuously, until the mixture is hot, opaque, and the sugar is completely dissolved (it should not feel gritty between your fingers), about 5 minutes.
Add the butter, a tablespoon at a time, whipping well after each addition. (If it begins to look curdled, continue to beat until it comes back together, before adding the remaining butter.)
If the melted chocolate seems too thick, it can be thinned with a few teaspoons of vegetable or canola oil.