Instructions

• Preheat the oven to 375°F. Line a 12-count muffin pan with paper liners and set aside.
• In a large bowl, whisk together 2 cups all-purpose flour, 1 teaspoon baking soda, and 1/2 teaspoon salt. Set the dry mixture aside.
• Place 4 ounces semi-sweet chocolate (chips or chopped) and 1/2 cup unsalted butter in a heatproof bowl. Melt together in the microwave in 20–30 second intervals, stirring between intervals, or melt gently on the stovetop. Stir until smooth, then let the chocolate-butter mixture cool about 5 minutes.
• In the bowl of an electric mixer (or a large mixing bowl), combine the cooled chocolate-butter mixture with 1 cup sugar and 1/4 cup cocoa powder. Add the 2 eggs, 2 teaspoons vanilla extract, and 1/4 cup sour cream. Mix on medium-low speed until well incorporated and smooth.
• Reduce the mixer speed to low. Gradually add the dry flour mixture to the wet ingredients and mix just until combined—do not overmix.
• Fold in 1 cup of the 1 1/2 cups dark chocolate chips, reserving the remaining 1/2 cup for topping.
• Divide the batter evenly among the 12 prepared muffin liners, filling each about 3/4 full.
• Bake at 375°F for 20 minutes, or until a toothpick or knife inserted into the center of a muffin comes out mostly clean.
• Remove the muffins from the oven and immediately sprinkle the reserved 1/2 cup dark chocolate chips on top of the hot muffins, pressing them lightly into the tops so they stick.
• Allow the muffins to cool in the pan for about 5 minutes, then transfer them to a wire rack to cool completely before serving.