With an electric mixer on medium-high speed, cream butter and brown sugar until pale fluffy
Add eggs, one at a time, beating until each is incorporated, scraping down sides of bowl as needed
Add flour mixture in three batches, alternating with two additions of buttermilk, and beating until combined after each
Divide batter evenly among lined cups, filling each three-quarters full
Bake, rotating tins halfway through, until golden brown and a cake tester inserted in centers comes out clean, about 25 minutes
Transfer tins to wire racks to cool 10 minutes; turn out cupcakes onto racks and let cool completely
Cupcakes can be stored up to 3 days at room temperature, or frozen up to 2 months, in airtight containers
To finish, place cupcakes on a wire rack set over a baking sheet; spoon icing over cupcakes and let set
Cupcakes are best eaten the day they are glazed; keep at room temperature until ready to serve
Brown Butter Icing
Melt butter in a small saucepan over medium heat, swirling pan occasionally, until nut-brown in color, about 10 minutes
Remove from heat, and pour butter into a bowl, leaving any burned sediment behind
Add confectioners' sugar, vanilla, and 2 tablespoons milk to brown butter; stir until smooth
If necessary, add more milk (up to 2 tablespoons) a little at a time, just until icing is spreadable Use immediately
Notes
Cooling. Always allow your cupcakes to cool for a few minutes in the muffin tin and then remove them to a cooling rack to finish cooling. The heat from the pan will continue to cook them so don’t leave them in there too long.Scooping. To make sure my cupcakes are all the same size I always use a scoop and fill the muffin tins 2/3 full. Don’t over fill your cupcakes.Ingredients. Be sure your ingredients are room temperature and they will combine more smoothly.