Preheat oven to 400℉/205℃. Line a 12 tin muffin liner with 12 liners or 2 liners with 6 muffin tins in each (Your preference) and set aside.
In a medium-sized bowl, sift the dry ingredients. Add in flour, sugar, baking soda, cocoa powder, baking powder, and salt. Gently mix together.
2 cups all-purpose flour, 1 1/4 cup white sugar, 1/2 cup unsweetened cocoa powder, 1 tsp baking soda, 2 tsps baking powder, 1/2 tsp salt
In a large bowl, whisk eggs, egg yolk, milk, sour cream, oil, and vanilla. Whisk until well combined (1-2 minutes).
2/3 cup vegetable oil, 2 large eggs, 1 egg yolk, 1/2 cup milk, 1 cup sour cream, 1 tbsp vanilla
Add in the dry ingredients. Using a spatula, gently fold until a batter forms. Do not over-mix!
Toss in the chocolate chips and mix in a few times.
3/4 cups semi-sweet chocolate chips
Evenly divide the batter between 12 liners, they should be almost or all the way full. Using a cookie scooper helps big time to minimize the mess. Sprinkle extra chocolate chips and white sugar on top for a crisp top.
Bake the muffins at 400°F for 15-18 minutes. The muffins are ready when they bounce back at touch or a toothpick inserted comes out clean.