Preheat oven to 425 degrees F. Spray a jumbo muffin pan with oil, add jumbo liners, and set aside.
In a large mixing bowl, add eggs, sugar, brown sugar, vegetable oil, melted butter, and vanilla extract. Whisk together until all ingredients incorporated. Then add sour cream, and buttermilk. Whisk everything together until smooth.
In a separate bowl, combine flour, salt, baking powder, baking soda, and nutmeg. Whisk together and add to the wet ingredients. Fold together until all of the flour is mixed in and then fold in chocolate chips.
Cover batter and allow it to rest for 15 minutes at room temperature.
Add a ½ cup of the batter to each muffin tin. Top with additional chocolate chips (optional). Bake at 425 degrees F for 5 minutes, then reduce the heat to 350 degrees F and continue to bake for 23-25 minutes, until a toothpick comes out clean.
Allow muffins to cool for 5-10 minutes before eating.