Preheat your oven to 325°F (160°C) and grease a standard loaf pan.

In a medium bowl, combine flour, cinnamon, granulated sugar, and brown sugar. Incorporate cold butter until the mixture resembles coarse breadcrumbs.

In a separate mixing bowl, whisk together flour, baking soda, and salt. Set aside.

Mix melted butter with both types of sugar until smooth, then add egg, vanilla extract, and sour cream. Whisk well.

Fold in the mashed ripe bananas into the wet mixture and stir gently until evenly distributed.

Gradually add the dry mixture to the wet ingredients and mix gently just until combined.

Pour half of the batter into the prepared loaf pan, sprinkle the cinnamon-sugar filling over it, and then add the remaining batter on top.

Spread the chilled crumble topping evenly over the last layer of batter.

Bake for 40-45 minutes until golden brown and a toothpick comes out clean.

Remove from oven, cool in the pan for 30-40 minutes, then drizzle with glaze made of powdered sugar and milk once cooled.