Choco-Sour Cream Cupcakes

INGREDIENTS

• 1 1/2 cups all-purpose flour
• 1/2 cup granulated sugar
• 1/2 cup dark brown sugar
• 3/4 teaspoon baking soda
• 1/4 teaspoon salt
• 2 ounces bittersweet chocolate, finely chopped
• 2 tablespoons unsalted butter, softened
• 1/4 cup unsweetened cocoa
• 1/2 cup boiling water
• 1/2 cup light sour cream
• 1/2 cup low-fat buttermilk
• 2 large eggs
• 1 batch Milk Chocolate-Cream Cheese Frosting