Preheat oven 200 C / 400 F. Line the 12-hole muffin tin with liners. Place liners in every other hole.
Place flour, sugar, baking powder and baking soda in a large bowl.
Whisk to combine.
Place eggs, milk, yogurt, oil and vanilla extract in another bowl. Whisk until combined.
Make a well in the middle of the flour mixture. Add egg mixture.
Whisk until just combined. Do not overmix.
Fold in 1 cup chocolate chips.
Rest the batter for 10 minutes.
Divide batter among the muffin liners. Make sure you fill to the top.
Top the muffins with extra chocolate chips.
Bake for about 20-25 minutes or until a skewer inserted to the center of the muffins comes out clean. Start with 7 minutes at 200 C/ 400 F, and then reduce the temperature to 180 C 350F for the remaining time.
Leave muffins in the tray to cool for 10 minutes before turning on to a wire rack to cool completely.