Preheat oven to 350 degrees F.
In a large bowl, sift the all-purpose flour, baking powder, baking soda, salt, and set aside.
Using an electric mixer, beat the unsalted butter, brown sugar, and granulated sugar until smooth.
Add the eggs, sour cream, vanilla extract, and melted chocolate.
Add the flour mixture alternating with the buttermilk.
Using an ice-cream scoop, scoop the batter evenly in your muffin tin and bake for 15-18 minutes.
To make the frosting, Using an electric mixer, beat the unsalted butter for 2-3 minutes or until smooth.
Add the vanilla extract, unsweetened cocoa powder, powdered sugar, and milk.
Mix for 4-5 minutes on medium-high speed for 3-4 minutes or until fluffy.
Using a piping bag, frost your cooled cupcakes and enjoy!
