Preheat your oven to 350 degrees
Grease and line a 9”x5” loaf pan with parchment paper
In a large bowl, whisk 4 tablespoons of softened butter with 1/4 cup brown sugar, 1/4 cup of granulated sugar, 1 teaspoon of vanilla extract, 1 teaspoon of ground cinnamon, 1/4 teaspoon of nutmeg, 1/4 teaspoon of cloves, 1/4 teaspoon of salt, 1 large egg and 2 tablespoons of sour cream until smooth
Add 2 large overly ripe mashed bananas into the bowl and mix until evenly distributed
Whisk in a cup of all purpose flour and a teaspoon of baking powder until mostly combined
Transfer the mixture into the prepared loaf pan
In a small dish, cut 3 tablespoons of cold butter into 1/2 cup of all purpose flour, 1/2 cup of brown sugar, 3/4 teaspoon of ground cinnamon and a pinch of salt until the butter is evenly distributed and in pea sized pieces
Transfer the streusel topping over the batter and sprinkle a tablespoon of coarse sugar over the streusel
Bake for 40-45 minutes or until a toothpick will come out of the center dry
Allow the loaf to cool for 15 minutes in the loaf pan placed over a cooling rack and then transfer the loaf directly into the cooling rack to continue cooling
Enjoy warm or at room temperature