Preheat oven to 180c/350F.
Line the loaf pan with parchment/baking paper and a light spray of spray oil.
Peel bananas and place in bowl. Use a fork or whisk to mash the bananas well until there are no large chunks.
Add in the egg, oil, milk and brown sugar. Whisk well.
Add in the rest of the ingredients (flour, bicarb soda, baking powder, salt).
Mix well until the mixture just comes together and there are no longer any clumps.
Place the Biscoff spread in the microwave for few seconds so it's runny.
Pour a third of the banana bread batter into the pan, then 1/2 the melted biscoff, then another third of the banana bread batter. Follow with the last 1/2 of the biscoff and the final third of batter.
Swirl with a butterknife or skewer
Pour the banana bread batter into the loaf pan and place in the oven for 50-55 minutes.
Banana bread is done when it is nicely browned on top. Place a skewer or knife in the highest part in the centre, if it comes out with wet batter, continue to bake for 5 minutes until the skewer comes out clean.
Allow to cool down completely before removing from the pan.