Preheat the oven to 375°F and lightly grease a 12-cup muffin tin with olive or coconut oil spray.

First, make the streusel. Melt 5 tablespoons of butter, then stir in the chopped pecans, flour, brown sugar, cinnamon, and salt. The mixture will look wet. Set it aside.

Melt the 3/4 cup of butter for the muffin batter and set it aside to cool slightly.

In a medium bowl, whisk the flour, baking soda, and salt together. Set aside.

In a large bowl, mash the overripe bananas with a fork. Add the brown sugar, melted butter, vanilla, and eggs, then whisk until combined.

Gradually add the flour mixture to the banana mixture, whisking or stirring gently just until no streaks of flour remain. Do not overmix.

Fold the chopped pecans into the batter. Fill each muffin cup just over halfway full.

Sprinkle the pecan streusel evenly over the muffins, using about 1 tablespoon per muffin. Bake for 18 to 20 minutes, or until a toothpick inserted in the center comes out with only a few moist crumbs.

Let the muffins cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.

While the muffins cool, make the optional glaze. Whisk the powdered sugar with milk until smooth, then stir in vanilla and cinnamon to taste. Drizzle over the cooled muffins and enjoy.