Preheat oven to 425 degrees. Spray or line a jumbo muffin tin, set aside.

In a large mixing bowl mix together the sugar, vegetable oil, melted butter, eggs and vanilla. Add the mashed banana and mix just until combined.

In a medium mixing bowl whisk together the flours, baking powder and salt. Alternate adding the dry ingredients and the buttermilk to the banana mixture. Fold in any chocolate chips or chunks. Do not overmix! The batter should look slightly lumpy.

Scoop or pour the batter into the prepared muffin tin. Fill each well 1/4" from the top.

Place in the oven and bake at 425 degrees for 5 minutes, then turn the heat down to 375 degrees and continue baking for an additional 25 minutes.

Remove from the oven and allow the muffins to cool in the tins for 15 minutes before removing and transferring to a wire rack to cool completely.