Banana Crumb Muffins

Bahan-bahan (12 porsi)

• 1 1/2 cups all-purpose flour
• 1 teaspoon baking soda
• 1 teaspoon baking powder
• 1/2 teaspoon salt
• 3 bananas (mashed)
• 3/4 cup white sugar
• 1 egg (lightly beaten)
• 1/3 cup unsalted butter (melted)
• 1/3 cup brown sugar (packed)
• 2 tablespoons all-purpose flour
• 1/8 teaspoon ground cinnamon
• 1 tablespoon unsalted butter