Start by browning the butter. You'll take a half cup (1 stick) of butter and melt in a medium saucepan, and then continue to cook past the point of boiling. You will do this over medium heat, past the point of the butter foaming, until it turns a nice golden brown, and has a nutty smell. Make sure you are stirring and watching it, because it will turn from perfectly brown to burnt fairly quickly. Once finished browning, pour into a bowl and allow to cool completely. I usually throw it into the freezer for 10 minutes.
½ cup salted butter
Preheat your oven to 350 degrees F. Spray a 9x5 loaf pan with nonstick spray, and/or line with parchment paper.
Mash your brown bananas in a large mixing bowl. Add in browned butter, sugars, eggs, vanilla and sour cream and whisk until all mixed together well.
1-1½ cups mashed ripe bananas, ⅔ cup granulated sugar, ⅓ cup brown sugar, 2 large eggs, ½ cup sour cream or greek yogurt, 2 teaspoons vanilla
Add flour, baking soda, salt, cinnamon and nutmeg and slowly mix, being careful not to over mix.
2 cups all purpose flour , 1 teaspoon baking soda, ¾ teaspoon salt, ½ teaspoon cinnamon, ⅛ teaspoon nutmeg
Pour half the batter into prepared pan. Sprinkle with the brown sugar and cinnamon mixture and then pour the remaining batter over the top of the mixture.
2 tablespoons brown sugar, 1 teaspoon cinnamon
In a small bowl mix together the flour, brown sugar, cinnamon and salt for the crumb topping. Add in the soft butter and work it together with a fork or your fingers until it starts to come together and almost look shaggy. Sprinkle it over the top of the bread batter.
⅓ cup all purpose flour, ¼ cup brown sugar, ½ teaspoon cinnamon, pinch of salt, 3 tablespoons salted butter
Bake for about 55-60 minutes. I always stick a toothpick into the center of the bread where it has cracked and looks more gooey. If it comes out clean, your bread is done.
Allow to cool for 15-20 minutes in the pan before removing. Cutting the bread when it's too warm will result in bread that starts to fall apart.