• Preheat the oven to 350℉. Line two 12-cup muffin pans with cupcake liners and set aside for later.
• Using a hand or stand mixer, beat the butter, sugar, and light brown sugar in a large mixing bowl until smooth and creamy.
  1/2 cup (1 stick) salted butter, 1/2 cup granulated sugar, 1/2 cup packed light brown sugar
• Beat in eggs and vanilla extract just until combined.
  2 large eggs, 1 teaspoon vanilla extract
• Add the mashed bananas and mix on low speed just until combined.
  3 ripe bananas
• In a separate smaller bowl, whisk together the flour, baking soda, and baking powder.

  Gradually add the dry ingredients into the wet ingredients and mix on low speed just until combined and no flour streaks remain.
  1¾ cups all-purpose flour, 1 teaspoon baking soda, ½ teaspoon baking powder
• Stir in the chopped walnuts.
  1 cup walnuts
• Scoop the muffin batter into the prepared muffin tins, filling each liner about 2/3 of the way full (a little over half full).

Make The Crunch Topping

• In a mixing bowl, using a hand or stand mixer, beat together the brown sugar, butter, and flour until combined.
  1/2 cup packed light brown sugar, 3 tablespoons salted butter, 2 tablespoons all-purpose flour
• Stir in the oats and chopped walnuts.
  2/3 cup whole old-fashioned oats, 2/3 cup walnuts
• Evenly divide the crunch mixture over top of each muffin.
• Bake for 20-25 minutes or until a toothpick inserted comes out clean and the tops bounce back when gently tapped.
• Allow the muffins to cool inside the warm muffin pan for 5-10 minutes before removing them to a cooling rack to cool completely.