375* oven. Grease your 12-cup muffin tin with Baker's Joy or Pam for Baking with Flour and set aside.
Melt HALF the chopped chocolate and all the butter in a microwave or in a bowl set over a pot of simmering water. Stir often to prevent scorching.
Grab a large bowl and whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and the salt until any lumps are broken up and the dry ingredients are fluffy and clump-free.
In another bowl, whisk the buttermilk, the egg, and the vanilla extract together until combined. Note: If you use a large measuring cup, you can measuring in the buttermilk, and then add in the egg, and the extract without dirtying an extra thing.
Add the buttermilk mixture and the melted butter mixture to the dry ingredients. Using a whisk or a rubber spatula, carefully stir to blend BUT before you completely mix in the flour, add in the last of the chopped chocolate. DO NOT try to get every last lump out of the mixture or your muffins will be flat and sad. The flour helps coat the chips or chunks and keeps them from sinking in the muffin.
Plop the batter equally in each of the muffin cups. Bake for 18-22 minutes or until a tester inserted into the middle of a muffin comes out clean. Press gently on the top of the muffin and it should bounce back (another sign of "doneness").
Move the tin to a wire rack and cool for five minutes before removing the muffins.
Wait until FULLY COOLED. Not WARM. Not LUKEWARM, but room temperature before storing your leftover muffins in a reusable plastic container. If you store them warm, the heat will make your muffins weirdly wet.