Mash 3 ripe bananas with a fork. Beat in 1 egg, and mix in the white and brown sugar. Add 1 teaspoon of vanilla extract, and mix in 1/3 cup of canola oil.
Sift together the flour, baking soda, baking powder, salt, and cinnamon.
Fold in the banana mixture with the flour mixture. Mix until just combined.
Preheat the oven to 190 degrees celsius. Start making the crumb topping; Combine 1/4 cup brown sugar with 2 tablespoons all purpose flour and 1/2 teaspoon of cinnamon. Cut in 1 tablespoon of cold butter until the mixture resembles course crumbs.
Grease or line a muffin pan. Spoon the batter into the tins. 3/4 full. Sprinkle the top of each muffin with 1 tablespoon of the crumb topping.
Bake at 190 degrees celsius for 18 minutes, or until a skewer inserted into the muffin comes out clean.
Leave the muffins to cool in the tins for 10-15 minutes. Slide a butter knife around the edges to remove, and place on a wire rack to cool completely.
