Preheat oven to 350F°. In a medium bowl, mash banana with a spoon or fork. If you have a little helper, you can assign this task to him or her. Add in brown sugar, egg and vanilla. Stir together. Pour in butter and mix until combined. Set aside.
In a large bowl mix remaining dry ingredients. Chop up strawberries into small pieces. You can use up to 3/4 cup if you want more strawberries per muffin. Transfer to flour mixture. Toss to coat fully.
Pour banana mixture in with strawberries and flour mixture. Fold wet and dry ingredients to combine. Do not over mix. Do so just until combined.
Using a large cookie scoop, divide evely between cups of a prepared muffin pan. I got 8 muffins out of this half recipe. If you do not have muffin liners, simply spray your pan with pam for baking. It will help your muffins to pop out easily after being baked. Top off with a sprinkle of sugar.
Bake for 20 minutes or until fully cooked. Use a toothpick or cake tester to check for doneness. Remove from oven, allow to cool in the pan for 5 minutes. Carefully transfer to a wire rack to cool completely.