In a large bowl, whisk together your dry ingredients.
Mix the egg, vanilla, oil, sour cream and bananas together in a large glass measuring cup.
Pout the wet ingredients into the dry, then mix together until they are almost completely combined, then add in the chocolate chips. Don't over-mix the batter.
Place into your lined or greased unlined muffin tins, filling about 3/4 of the way full, and bake at 375 degrees until beautifully browned, around 8-10 minutes.
Notes
You don't have to add in the chocolate chips but if you do use mini and not large!
If you use fruit in mini muffins, make sure it's small (eg small blueberries or chopped strawberries)