• Preheat the oven to 350°F. Line a cupcake pan with 6 cupcake liners.
• In a medium bowl, whisk together the flour, cocoa powder, sugar, baking soda, baking powder, and salt.
• In a separate bowl, whisk together the egg, oil, milk, and vanilla extract until smooth.
• Add the dry ingredients to the wet ingredients and mix until just barely combined.
• Add in the hot coffee and mix until the chocolate cupcake batter comes together. Do not overmix.
• Divide the batter evenly between the 6 cupcake liners. Bake for 14–16 minutes, or until a toothpick inserted into the center of the cupcakes comes out clean.
• Let the cupcakes cool on a wire rack completely.

Vanilla buttercream:

• In a microwave safe bowl melt the bittersweet chocolate and let it cool until just warm. Once warm add in the butter and whip until light and fluffy. Scrap the bottom and sides of the bowl.
• Add in the powdered sugar, sour cream, salt and vanilla extract. Mix for 1 to 2 more minutes. Continue to cream until light and fluffy.
• Place the chocolate buttercream in a piping bag with desired piping tip and pipe frosting onto cooled cupcakes and enjoy!