Banana Chocolate Chip Muffins

5 tablespoons butter (melted and cooled slightly)
1 1⁄2 cups flour
1⁄2 cup brown sugar
1 teaspoon baking powder
1 teaspoon baking soda
1⁄4 teaspoon salt
3 bananas (ripe, mashed)
1 egg (large)
1⁄2 teaspoon vanilla extract
3⁄4 cup chocolate chips (mini or regular size)

Heat oven to 350 degrees F. Line muffin cups with paper liners. Whisk the flour, brown sugar, baking powder, baking soda, and salt in a large bowl. In another bowl, whisk the melted butter, mashed banana, egg, and vanilla until blended. Add the banana mixture to the bowl with dry ingredients then use a fork to combine. Do not over mix. Stir in chocolate. Fill muffin cups 3/4 full. Bake until a toothpick can be inserted and come out clean, about 18-20 minutes.