• Preheat oven to 425F (220C) and line a muffin tin with paper liners*
• Place peeled bananas in a large bowl and use a fork or a potato masher to mash them - bananas should be well-mashed.
• Add canola oil and melted butter and stir well.
• Stir in sugars until well-combined.
• Add eggs and vanilla extract and buttermilk and stir well. Set aside.
• In a separate bowl, whisk together your dry ingredients -- flour, baking powder, baking soda, and salt.
• Add dry ingredients to your wet batter and gently fold in until ingredients are just combined (don't over-mix the batter!).
• Portion batter into prepared muffin tin, filling each liner 3/4 of the way full. Set aside and prepare your Streusel topping.

Streusel Topping (optional)

• Combine flour, brown sugar, and salt in a medium-sized bowl and use a fork to stir the ingredients together.
• Using a pastry cutter, cut in your cold butter until the butter is well-worked in and your mixture resembles coarse crumbs.
• Sprinkle streusel topping evenly over each muffin.
• Bake muffins on 425F (218C) for 8 minutes and then reduce the oven temperature to 350 (175C) (do not open the oven door or remove the muffins, just leave them in and reduce the temperature) and bake another 7-8 minutes on 350F (177C). A toothpick inserted in the center of the largest muffin should come out clean or with few moist crumbs (no wet batter) to test for doneness.
• Allow muffins to cool before enjoying.