Preheat oven to 375F and prepare muffin trays with liners (spray with non-stick spray if desired). Whisk flour, granulated sugar, cocoa powder, baking powder, salt and baking soda in a medium bowl. In a large bowl whisk together the eggs, Greek yogurt, vegetable oil, milk and vanilla until well blended. Add dry ingredients to the wet ingredients and stir just until combined.

Mix in 1 1/2 cups of the chocolate chips, leaving 1/2 cup for sprinkling the tops of the muffins. Evenly fill 18 muffin cavities (a little more than 3 tbsp) then sprinkle with a few more of the chocolate chips. Bake for about 18 minutes or until a toothpick inserted into the center has a few moist crumbs. Place the trays on cooling racks for 5-10 minutes then transfer muffins to cool completely.