Preheat the oven to 350℉ (175℃). Lightly grease an 8-inch (20cm) or 9-inch (22 cm) loaf pan and line it with an overhang of baking paper.
Combine room temperature milk and vinegar in a bowl and let it sit for 10 minutes until slightly curdled.
Add sugar, vanilla and oil to the milk mixture. Mix with a hand whisk until sugar is dissolved.
Add mashed banana and mix until combined.
Add all the dry ingredients (flour, baking powder, baking soda, salt and cinnamon) into liquid ingredients, mix until fully combined and the batter is smooth.
Pour the batter into the pan and score the batter by running a small knife about 1/4 inch deep in the batter from one end of the pan to the other end. This will encourage the batter to cook and rise more evenly. Add a thick layer of crumble topping.
Bake for 40-45 min or longer if needed. Test the middle of the banana bread with a skewer. It should come out clean with a little crumb.
Let it cool in the loaf pan for 45 min and then carefully remove the loaf and allow it to cool on a cooling rack.
Drizzle melted Biscoff (cookie butter) spread all over the cake.
Portion into thick slices and enjoy. Store the bread in an air tight container. It will be more moist on the following day!