Preheat the oven to 350°F and line a muffin pan with cupcake liners.
Whisk flour, baking powder, baking soda, and salt until well combined.
Beat softened butter and sugar for about 3 minutes until pale and fluffy.
Add eggs one at a time, then mix in the vanilla until smooth.
Add half the dry mixture, then the milk, then the rest of the dry mixture; mix until smooth and thick.
Fill liners ⅔ full and bake for 18–20 minutes, then cool for 20 minutes.
Tint frosting in red or green for hats and keep some white for beards; chill briefly if too soft.
Pipe the hat, add a candy nose, and use white frosting or sprinkles to create the beard.