Preheat oven to 350 degrees. Butter two 8x4-inch bread pans; set aside.

BANANA BREAD: In a small bowl, mash bananas, with 2 tablespoons brown sugar, vanilla extract, and 3/4 teaspoon cinnamon; set aside.

In a medium bowl, whisk together 2 cups flour, baking powder, baking soda, and salt; set aside.

In a large bowl, using an electric hand mixer, beat 1/2 cup softened butter and granulated sugar together until light and fluffy. Add eggs one at a time beating well after each addition. Add sour cream, beat until just combined.

Gradually add flour mixture to the large bowl, beating until just combined. Add mashed banana mixture, beat until just combined.

Divide batter evenly into the prepared pans.

CRUMB TOPPING: In a medium bowl, whisk together, 1 cup brown sugar, 1 cup flour, and 1 teaspoon cinnamon. Cut in a 1/2 cup cold butter with a pastry cutter until the topping resembles coarse crumbs.

Sprinkle the topping evenly over the batter in both pans squeezing some of the topping in your hands, creating bigger crumbles.

Bake for 40-45 minutes or until a toothpick inserted into the middle comes out clean with a few crumbs stuck to it. Allow bread to cool in the pan for 10 minutes before removing to a cooling rack. Slice and enjoy!