For the toppping
1. Heat the butter in a pan, add the onion and green chilli and sauté till the onion is translucent.
2. Add the mushrooms and plain flour and sauté for a further 2 minutes.
3. Gradually add the milk, while stirring continuously so that no lumps form. Bring to a boil.
4. Add the cheese, mustard, black olives, salt and pepper and mix well.
5. Allow it to cool and keep aside.
How to proceed
1. Cut the bread into 50 mm. (2") diameter circles, using a cookie cutter. You will get about 12 circles.
2. Lightly butter each bread circle on one side.
3. Arrange the buttered bread circles on a baking tray and bake in a pre-heated oven at 180°C (360°F) for 2 to 3 minutes.
4. Spread the topping mixture generously on top of each bread circle. Bake in a pre-heated oven at 180°C (360°F) for 2 to 3 minutes.
5. Serve hot.