Preheat oven to 375 degrees. Line a cupcake tin with paper liners, set aside.
In a large bowl, whisk flour, sugar, both cocoa powders, baking soda, and salt. Set aside. In the bowl of your stand mixer fitted wight he paddle attachment, beat egg, buttermilk, vegetable oil and vanilla together until thoroughly combined. Slowly pour in dry ingredients and stir until smooth. Pour in hot coffee and mix until completely smooth. Batter will be very runny.
Divided batter among prepared cupcake liners no more than 2/3 full (the batter will rise over and create a huge mess!). Bake for 20-25 minutes or until a toothpick inserted in the center comes out moist with a few crumbs. Tops should slightly spring back when touched. Allow cupcakes to cool for about 10 minutes in hot pans so they have time to set up and be easier to handle before transferring to wire racks to finish cooling. While cupcakes are cooling, prepare frosting.
Add raspberries to a food processor and pulse until pureed. Push through a mesh strainer and discard seeds. Set aside.
Beat butter until smooth with no lumps. Scrape the sides as needed and add confectioner's sugar, raspberry puree and champagne. Beat until combined, about three minutes or until light and fluffy. If the frosting is too thin or it looks a little separated (from the carbonation in the champagne), add up to 1/2 cup more sugar to thicken it up. Frost cooled cupcakes. If you use less frosting than I did, you may have some extra. It makes just enough for 14 cupcakes.
Dark Chocolate Cupcakes with Raspberry Champagne Frosting will stay fresh for up to three days stored in an airtight container. The cupcakes will last for 7 days but the frosting is only good for three.