Preheat oven to 350ºF.

In a large mixing bowl, cream brown sugar, eggs, and butter together until fluffy.

Add cocoa powder and boiling water. Beat again.

Add flour and baking soda. Beat well until batter is smooth.

Add sour cream. Beat until batter is uniform throughout.

Transfer batter into cupcake liners.

Bake for 25 minutes or until a toothpick comes out cleanly. Allow cupcakes to cool completely before frosting.

To prepare frosting, in a medium mixing bowl, cream butter and powdered sugar together.

Add 2 tablespoons of milk and vanilla. Beat well.

If it is too thick, add more milk. If it is too thin, add more powdered sugar.

Add brown coloring gel to frosting and beat until desired color is reached.

Transfer frosting to a ziplock bag and cut the corner off.

Pipe frosting onto cupcakes.

Break pieces of pretzels off to create antlers.

Add antlers, eyes, and noses to cupcakes to create reindeer.