1. Line 18 greased muffin tins with thinly sliced bread slices, removing the crusts.
2. Spread bread slices with soft butter - it is easier to use the back of a spoon rather than a knife.
3. Bake at 200^oC for about 8-10 mins. till crisp.

For Filling :

1. Fry the chopped onions in 1 tbsp. butter till soft.
2. Add chopped capsicum, chopped celery and cooked corn kernels. Take off fire.
3. Add the white sauce, grated cheese, salt, pepper and mustard to taste.
4. Pour the mixture into the bread cups.
5. Sprinkle a little more grated cheese on top.
6. Bake at 180^o C for about 10 mins.
7. Serve hot with chilli sauce.