Special equipment: 12 muffin cups
Preheat oven to 350 degrees F.
Sift the flour, baking powder, baking soda and salt together onto a sheet of parchment paper.
In a large bowl beat the eggs, yolks and sugar together. Add the melted butter, vanilla and buttermilk to the mixture.
Add the dry ingredients gradually into the batter. Mix until smooth. It will appear light and fluffy.
Ladle and divide the batter evenly among muffin cups and bake for about 18 minutes, or until a toothpick tester comes out clean. Let cupcakes cool on a wire rack for 15 minutes before frosting.
For the frosting: Beat the butter and cream cheese until creamy. Add confectioners' sugar slowly, while mixing in melted chocolate and vanilla extract.