Preheat your oven to 375F degrees. Put muffin liners into a standard 12 cup muffin tin, set aside.
In a large mixing bowl or with your electric mixer, add in the bananas and mash well. Add in the sugars, milk, and coconut oil. Mix until everything is combined.
Add in the cinnamon, flour, baking soda, baking flour, and salt. Don't over mix but make sure everything is combined.
Scoop about ¼ cup of batter into the lined muffin tin.
In a separate bowl, it is time to make the topping. Mix the flour, sugar, and cinnamon. Once mixed, use a pastry cutter or fork and cut the cold butter into the topping mix. Once it all comes together in a crumble, sprinkle on the top of each muffin batter.
Bake for 15-17 minutes, but make sure to not over bake. To make sure the muffins are cooked through, use a toothpick and make sure it comes out clean.