Preheat the oven to 350°F (175°C).
Grease and line a muffin tin with cupcake liners.
In a bowl, cream together the butter and sugar until light and fluffy.
Add eggs one at a time, mixing well after each addition.
Stir in the vanilla extract.
In a separate bowl, whisk together flour, cocoa powder, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture until just combined.
Divide the batter evenly among the muffin cups.
Bake for 20-25 minutes, or until a toothpick comes out clean.
Allow to cool completely before decorating.