Preheat your oven to 350°F (175°C).

Grease and line a 9x13-inch baking dish with parchment paper, leaving a slight overhang for easy removal.

In a large mixing bowl, whisk together the melted butter and granulated sugar until smooth.

Add the eggs, mashed bananas, and vanilla extract, mixing until well combined.

In a separate bowl, whisk together the flour, baking soda, and salt.

Gradually add the dry ingredients to the wet mixture, stirring until just combined. Avoid overmixing.

If using, fold in the chopped nuts for added texture.

Pour the batter into the prepared baking dish and spread it evenly.

Bake for 25–30 minutes, or until a toothpick inserted into the center comes out clean.

Let the brownies cool completely in the pan before adding the glaze.

In a small saucepan, melt the butter over medium heat.

Remove from heat and whisk in the powdered sugar, milk, and vanilla extract until smooth and pourable.

Pour the glaze over the cooled brownies, spreading it evenly with a spatula.

Allow the glaze to set at room temperature for about 15–20 minutes before slicing.

Lift the brownies out of the pan using the parchment overhang, slice into 16 bars, and serve.