Shell prawns. Heat butter in pan, add peeled and finely chopped onion and crushed garlic, sauté gently until onion is golden brown. Add flour and curry powder, stir 2 minutes, remove pan from heat. Add water, stir till combined. Return pan to the heat, stir until sauce boils and thickens.
Add crumbled stock cubes, peeled and finely chopped apple, chopped banana, salt and pepper to taste, tomato sauce and vinegar; reduce heat, simmer covered 30 minutes. Remove lid from the pan and simmer a further 15 minutes or until sauce is thick. Press mixture though a sieve, return to the pan, add prawns and cream, simmer for 2 minutes. Pour into ovenproof dish. Melt extra butter in pan, add breadcrumbs, stir until combined. Sprinkle over the prawns. Bake in a hot oven 5 minutes or until crumbs are golden.