Dark Chocolate Cupcakes
8 Tbsp unsalted butter, cut into 4 pieces
2 oz. bittersweet chocolate, chopped
1/2 cup Dutch-processed cocoa
3/4 cup AP flour
1/2 tsp baking soda
3/4 tsp baking powder
2 large eggs
3/4 cup sugar
1 tsp vanilla extract
1/2 tsp table salt (1 tsp kosher)
1/2 cup sour cream
Adjust oven rack to lower-middle position; heat oven to 350. Line standard-sized muffin pan with cupcake papers.
Combine butter, chocolate, and cocoa in a medium heatproof bowl. Set bowl over saucepan containing barely simmering water; heat mixture until butter and chocolate are melted and whisk until smooth and fully combined. Set aside to cool until just warm to touch.
Whisk flour, baking soda, and baking powder in a small bowl to combine.
Whisk eggs in another medium-sized bowl. Add sugar, vanilla, and salt. Whisk until fully integrated. Add cooled chocolate mixture and whisk until combined. Sift about one-third of the flour mixture over the chocolate mixture and whisk until combined; whisk in sour cream until combined, then sift the remaining flour mixture over and whisk until batter is homogenous and thick.
Divide batter evenly among muffin pan cups. Bake until skewer inserted into center of cupcakes comes out clean, 18 to 20 minutes.
Cool cupcakes in muffin pan on wire rack until cool enough to handle, about 15 minutes. Carefully lift each cupcake from muffin pan and set on wire rack. Cool to room temperature before icing, about 30 minutes.