Preheat the oven to 425 degrees
Whisk together the dry ingredients in a mixing bowl: flour, baking powder, baking soda, and salt
In a separate bowl, whisk together the eggs, sour cream, vanilla extract, milk, sugar, and melted butter
Add the dry ingredients to the wet ingredients until just combined
Fold in the chocolate chips gently with a rubber spatula
Line a regular muffin tin with 12 parchment paper muffin liners
Distribute the chocolate chip muffin batter evenly
Top with additional chocolate chips and sprinkle with coarse sugar
Bake the chocolate chip muffins at 425 degrees for 5 minutes, then reduce the oven temperature to 350 degrees (do not open the oven door or remove the muffins) Bake the muffins at 350 for another 13-15 minutes, until a toothpick inserted comes out clean