Preheat your oven to 350°F (175°C) and grease two 8x4-inch loaf pans.

Mash 3-4 ripe bananas in a bowl, then mix in brown sugar, vanilla extract, and ground cinnamon.

Cream together the softened butter and sugar until light and fluffy, about 3-5 minutes.

Beat in the eggs one at a time, mixing well after each addition until smooth.

Sift the flour, baking soda, and salt together, then gently stir into the butter mixture and fold in the sour cream and banana mix.

Prepare the crumb topping by mixing flour, brown sugar, and cinnamon, then cutting in cold butter until coarse crumbs form.

Divide the batter into the loaf pans, sprinkle crumb topping evenly over each loaf.

Bake for 35-40 minutes or until a cake tester comes out clean.

Let the bread cool in pans for 10 minutes, then transfer to a wire rack to cool completely before slicing.