Preheat oven to 350°Line 2 muffin tins (24 cavities) with paper liners
Whisk together the flour, baking powder, baking soda and salt, in a medium bowl. Set asideIn a large heatproof bowl if you can, use the bowl stand-up mixer), combine the unsweetened chocolate and the cocoa powder.Heat the water and butter in a small saucepan, until butter is melted, but water is just simmering, not boiling.Pour the hot liquid over the chocolate and cocoa powder and stir until melted and smooth.Add the sugar and mix to combine.
If you have used a glass or ceramic bowl, from your stand up mixer, go ahead and put that on the mixer base and fit the mixer with the paddle attachment. If you used a different bowl, transfer the mixture to your stand up mixer or use a hand electric mixer.Making sure that the chocolate mixture is cool enough, start adding the eggs, one at a time, and beat until just combined.Add in the vanilla.Alternating with the buttermilk, add flour into chocolate egg mixture. You want to start and finish with the flour. DO NOT OVERMIX. This is where tough cakes come from.Be sure to scrape down sides and you can finish mixing with a spatula.
Use an Ice cream scoop to evenly distribute batter into muffin tins. I use a 2-1/2 oz scoopBake for 230-35 minutes, until toothpick comes out with just a few moist crumbs.Cool in pan for 10 minutes, then invert on to a cooling rack. Cool completely before frosting.
Frosting
In the bowl of a stand up mixer, fitted with the paddle attachment, cream the butter until light in color and fluffy.With mixer on low, slowly add the sugar. Scrape down the sides.Add in vanilla and beat until smooth.. Don't forget to check the underneath of the frosting.Frost each cupcake and decorate with fun sprinkles