Preheat oven to 425?F (218?C). Generously grease a jumbo 6-count muffin pan or line with muffin liners. Set aside.

Whisk the flour, baking powder, baking soda, salt, cinnamon, and nutmeg together in a large bowl. Set aside.

Whisk the melted butter, oil, sugar, and eggs together until combined. Then whisk in the sour cream, milk, and vanilla extract until the mixture is pale yellow.

Pour wet ingredients into dry ingredients and fold together with a spatula until completely combined. Use a whisk to rid any large lumps of flour, if needed, but avoid overmixing. Fold in the chocolate chips.

Divide batter between each muffin cup, filling all the way to the top. Sprinkle with coarse sugar if desired.

Bake at 425?F for 5 minutes, then reduce the oven temperature to 350?F (177?C) and continue to bake for 25-26 minutes until the tops are lightly golden and centers are set. Test for doneness with a toothpick.

Allow to cool for 10 minutes in the pan before serving.

Cover leftover muffins and store at room temperature for 5 days or in the refrigerator for 1 week. Muffins freeze well for up to 3 months; thaw in the refrigerator or on the counter.