Adjust oven rack to middle position and preheat to 350°F. Line cupcake pan with papers. Or cake pans.

Place bittersweet chocolate in large bowl and stir in hot coffee to melt. Whisk in 1/2 cup sour cream, sugar, oil, egg, and vanilla until combined.

Whish together flour, cocoa, salt, baking soda, and baking powder to the bowl. Whisk in wet ingredients just until smooth.

Divide batter between cups and bake until center is just firm, about 17 minutes. Let cupcakes cool in pan for 5 minutes, then transfer to cooling rack.