
Preheat the oven to 350 degrees F. Line a 12-cup muffin tin with paper liners and set aside.
In a medium bowl, whisk together the oil, granulated sugar and brown sugar. Add the eggs, buttermilk and vanilla and mix until very well combined.
Add the flour, baking powder, salt, and baking soda and before mixing, add the chocolate chips on top.
Mix the batter with a rubber spatula until no dry streaks remain (don't over mix or the muffins might be dry and tough).
Scoop the batter evenly into the muffin tin (about 2/3 full). If you have leftover batter and are worried about overfilling the muffin cups, bake a 2nd batch with the remaining batter.
Sprinkle the tops of the muffins with coarse sugar, if using. Bake for 18-20 minutes until the tops spring back lightly to the touch and/or a toothpick comes out clean or with a few moist crumbs.