Ingredients

For the cupcakes:
• ¾ cup unsweetened Dutch-process cocoa powder
• ¾ cup hot water
• 3 cups all-purpose flour
• 1 tsp. baking soda
• 1 tsp. baking powder
• 1¼ tsp. coarse salt
• 1½ cups (3 sticks) unsalted butter
• 2¼ cups sugar
• 4 large eggs, at room temperature
• 4 tsp. vanilla extract
• 1 cup sour cream, at room temperature
For the frosting:
• 14 oz. bittersweet chocolate, finely chopped
• 9 oz. cream cheese, at room temperature
• 9 tbsp. unsalted butter, at room temperature
• 3 cups confectioners' sugar, sifted
• 6 tbsp. unsweetened Dutch-process cocoa powder
• Pinch of salt
• 1 cup plus 2 tbsp. sour cream

Instructions

For the cupcakes:
• Preheat oven to 350 and line 2 standard muffin pans with paper liners.
• In a small bowl, mix cocoa powder and hot water until a thick paste forms. Set aside.
• In a medium bowl, whisk together flour, baking soda, baking powder, & salt. Set aside.
• Melt butter in a medium saucepan. Add sugar and stir until well combined.
• Transfer the butter & sugar mixture to the bowl of a stand mixer fitted with paddle attachment.
• Beat on medium-high for 4-5 minutes or until mixture has cooled.
• Add eggs one at a time and mixing well in between.
• Add vanilla and cocoa mixture, beat until well incorporated.
• With the mixer on low, alternate adding flour mixture and sour cream in two batches. Mix until just combined.
• Divide the batter evenly between the cupcake tins. Note: to do this without making a mess, I scooped the batter into a large ziplock back, cut off the tip, and piped the batter into the paper liners.
• Bake for 15-17 minutes, or until a toothpick inserted into the center comes out clean. Note: my first batch was too close to the top of the over and the cupcake tops cooked too quickly and cracked. I would recommend baking one pan at a time in the middle rack of the oven to avoid this.
For the frosting:
• Melt the chocolate in the microwave in a heat-proof bowl. Set aside to cool until just barely warm.
• In the bowl of a stand mixer fitted with the paddle attachment, beat the cream cheese and butter on medium-high until pale and fluffy, about 3-4 minutes.
• Gradually mix in the confectioners' sugar, cocoa powder and salt.
• Beat in the melted and cooled chocolate and then the sour cream.
• Mix until smooth.