Heat oven to 350 F.
Place sifted flour into a mixing bowl, add the baking powder, baking soda and salt and mix very well.
Add the grated Parmesan cheese and stir to incorporate into the flour mixture.
Add the stick of melted butter, stir.
Add the beer and stir until it is absorbed and you have a thick, sticky mixture, remotely resembling batter and much more similar to dough.
Grease a 12 cup muffin tin.
Using two soup spoons fill each cup with mixture (you should use half of the quantity you mixed).
Wrap the mozzarella balls/pieces in basil leaves and place in the center of each cup.
Using the soup spoons add more batter in each cup, covering the mozzarella and using up the rest of the mixture.
Gently press the batter around the rim of each muffin cup to seal the mozzarella and basil and prevent the cheese from oozing out as it melts.
Add the 12 pieces of butter, one on top of each batter filled muffin cup.
Place the entire muffin tin over a baking sheet and then place in the oven (this is necessary because the butter might leak a little bit on the sides of the tin as it melts)
Bake for 20-22 min, depending on your oven. When golden brown and a toothpick comes out clean, remove from oven.
While the muffins are cooling off, brush with the 1/2 stick melted butter.
When they have cooled off enough to touch, serve and enjoy immediately.