Start by preheating your oven to 350°F (175°C) and prepare a standard loaf pan by greasing it lightly with butter or lining it with parchment paper.

In a medium saucepan over medium heat, melt ½ cup of unsalted butter and cook until it turns golden brown and develops a nutty aroma.

In a large mixing bowl, mash three ripe bananas until smooth, then add the cooled brown butter, granulated sugar, brown sugar, eggs, and vanilla extract. Mix until well combined.

In a medium bowl, whisk together all-purpose flour, baking soda, baking powder, and salt. Set aside.

Gradually add the dry ingredients to the banana mixture, folding gently until just combined.

Gently fold in 3 tablespoons of white miso paste into the batter until evenly incorporated.

Pour the batter into the prepared loaf pan and bake for 50-55 minutes or until a toothpick inserted comes out clean.

Let the bread cool in the pan for 10-15 minutes before moving it to a wire rack to cool completely before slicing.