Step 1

Preheat oven to 425°F/220°C. Line the muffin pans with cupcake liners.

Step 2

In a medium bowl, mix all-purpose flour, cocoa powder, baking powder, baking soda, and salt until well combined.

Step 3

In a large bowl, whisk together vegetable oil, granulated sugar, eggs, milk, vanilla extract, and sour cream until well combined.

Step 4

Sift in the dry ingredients into the wet ingredients and stir until well incorporated. Fold in 1 1/2 cups of chocolate chips into the batter.

Step 5

Spoon the batter evenly into each cup or liner, filling each all the way to the top. Distribute the remaining 1/2 cup of chocolate chips evenly over the muffin tops, pressing them lightly into the batter.

Step 6

Bake the muffins for 5 minutes at 425°F/220°C. Then, keeping the muffins in the oven, reduce the oven temperature to 350°F/180°C. Bake for an additional 15-17 minutes or until a toothpick inserted in the center comes out clean.

Step 7

Allow the muffins to cool for 5 minutes in the muffin pans, then transfer to a wire rack to continue cooling.