Line a muffin pan with paper liners and set aside.

In your mixing bowl, combine gluten-free flour, xanthan gum, sugar, baking soda, and salt and set aside.

In a medium saucepan, combine butter, cocoa, and 1 cup water. Bring just to boiling, whisking constantly. Remove from heat and add to dry ingredients, beat until combined.

Add buttermilk, eggs, and vanilla and beat for one minute on low-medium speed.

Pour batter into cupcake liners. I use a large scoop that measures about 1/3 cup batter into each opening and get 24 cupcakes.

Bake at 350° for 17 minutes or until a toothpick comes out clean or with a few crumbs (no wet batter).

Let cool in pan for 4 minutes, then remove cupcakes to a cooling rack. Wait to frost until completely cool.

In a large mixing bowl, beat together butter and brown sugar until light and fluffy (several minutes). Add the salt, milk, and pure vanilla extract and until well blended. Add in the powdered sugar, 1 cup at a time, blending well after each addition.

Stir in semi-sweet mini chocolate chips. Spread onto cooled cupcakes or put into piping back and pipe onto cooled cupcakes.

Optional: top each decorated cupcake with a gluten-free mini chocolate chip cookie.

If you aren't consuming on the day you bake these, I'd recommend placing them in a refrigerator overnight and pulling out an hour before serving to allow to come to room temperature.