Beat softened butter and sugar in the bowl of an electric (or hand) mixer until smooth.
Add the egg, sour cream and milk.
Add the dry ingredients and beat until well combined.
Preheat oven to 425 degrees and using a small cookie scoop, divide evenly amongst mini cupcake liners in your mini muffin pan. Do not overfill.
Bake for 8-10 minutes or until a toothpick inserted comes out clean.
Allow to cool in the pan slightly before removing to a cooling rack. Enjoy immediately, or cool completely and freeze in a single layer in an freezer safe covered dish.