Preheat oven to 350F°. Line a muffin tin with 12 liners, set aside.
In a large bowl, whisk together dry streusel topping ingredients. Mix in melted butter until well incorporated and large clumps form. Transfer to a rimmed baking sheet. Break up into no larger than pea size clumps. Set aside.
In a large bowl or stand mixer, cream together butter and sugars until light and fluffy. Mix in eggs, followed by mashed banana, mixing until smooth. With mixer running on low, mix in salt, baking powder, baking soda and 1/2 cup of flour at a time until all flour has been incorporated. Mix only until no streaks remain.
Divide batter between prepared liners, using one large cookie scoop per. Sprinkle well with prepared streusel topping.
Bake for 20-25 minutes or until only a few moist crumbs cling to a toothpick inserted.
Allow to cool in pan for several minutes before transferring to a wire rack to cool completely.
Meanwhile, whisk together powdered sugar and milk. Drizzle over cooled muffins.
Store in an airtight container for up to several days.
Nutritional information is provided as a courtesy and is an estimate only. Nutrition information can vary for a variety of reasons. For the most accurate data, use your preferred nutrition calculator with the actual ingredients you used to make this recipe.
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