Peel and mash 3 very ripe bananas in a large mixing bowl until mostly smooth, leaving a few small lumps for texture (2-3 minutes).

Add ½ cup of melted unsalted butter, ¾ cup of light brown sugar, 2 large eggs (at room temperature), and 1 teaspoon of vanilla extract to the mashed bananas. Whisk until combined (about 2 minutes).

In a separate bowl, whisk together 1½ cups of all-purpose flour, 1 teaspoon of baking soda, and ¼ teaspoon of salt. Gently fold this dry mixture into the wet ingredients.

Warm ½ cup of Biscoff cookie butter in the microwave for 15-20 seconds. Gently fold it into the batter, leaving some streaks for visual appeal.

Grease a 9x5 loaf pan and pour the batter in evenly. Dollop any leftover Biscoff cookie butter on top and gently swirl it into the batter with a knife.

Preheat your oven to 350°F (175°C) and bake the loaf for 55-60 minutes. Check for doneness with a toothpick.

Let the bread cool in the pan for about 10 minutes before transferring to a wire rack. Allow it to cool completely (about 30 minutes).