# Take a banana and slice it up into an over proof bowl.
# In a separate bowl, rub a small amount of butter into flour with your fingers until the mix looks like rough breadcrumbs. (The amount you use will depend on how many crumbles you want to make. My tip is to start with as little butter as possible and add a little more until you reach a breadcrumb consistency).
# Stir a small amount of brown sugar into the flour / butter mix.
# Sprinkle the crumble topping on top of the banana.
# Bake the lot in the over (220C for about 15 minutes), or until the top of the crumble is golden brown.