In a bowl, combine the flour, chopped Biscoff cookies, brown sugar, rolled oats, ground cinnamon, and fine salt.
Cut in the cold butter using a pastry cutter or your fingers until the mixture resembles coarse crumbs. Set aside.
Preheat your oven to 350°F. Grease a 1.5 lbs (10x5x3) loaf pan or line it with parchment paper.
In a large bowl, mash the ripe bananas until smooth.
Stir in the melted butter until well combined.
Add the granulated sugar, eggs, vanilla extract, and sea salt. Mix until fully incorporated.
Stir in the sour cream and biscoff spread and baking soda.
Gradually add the flour, mixing until just combined.
Stir in chopped Biscoff cookies until evenly distributed.
Pour the batter into the prepared loaf pan and smooth the top.
Sprinkle the Biscoff streusel topping evenly over the batter.
Bake for 70-75 minutes, or until a toothpick inserted into the center of the bread comes out clean. Note: at the 50 minute mark, loosely cover with foil and continue to bake. this will prevent the top from over browning.
Allow the bread to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.
