Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners.
Whisk the flour, sugar, cocoa powder, baking powder, baking soda and salt together in a large bowl.
1 3/4 cups all-purpose flour, 1 cup granulated sugar, 2/3 cup unsweetened cocoa powder, 2 teaspoons baking powder, 1/2 teaspoon baking soda, 1/2 teaspoon salt
In a separate bowl, whisk together the eggs, milk, sour cream, oil, and vanilla. Add to the bowl of dry ingredients, stirring just until combined.
2 large eggs, 3/4 cup milk, 3/4 cup sour cream or Greek yogurt, 1/2 cup vegetable oil, 2 teaspoons vanilla extract
Stir in 1 and 1/2 cups of the chocolate chips, reserving 1/2 cup for sprinkling over the tops of the muffins.
2 cups semisweet chocolate chips
Divide the muffin batter evenly between the muffin cups, filling them almost to the top. Sprinkle with a few chocolate chips on each muffin.
Bake for 15-17 minutes until a toothpick inserted into the center of a muffin comes out mostly clean with just a few crumbs. Do not overbake.