Chocolate Stout Cupcakes

INGREDIENTS

• 3/4 cup unsweetened cocoa, plus more for dusting finished cupcakes
• 2 cups sugar
• 2 cups all-purpose flour
• 1 teaspoon baking soda
• Pinch fine salt
• 1 12 ounce bottle stout beer, at room temperature (recommended: Guinness)
• 1 stick butter, melted
• 1 tablespoon vanilla extract
• 3 large eggs, at room temperature
• 3/4 cup sour cream
• 1 (8-ounce) package cream cheese, softened at room temperature
• 3/4 to 1 cup heavy cream
• 1 (1-pound) box confectioners' sugar