1. Melt the butter in a saucepan, add the onions and simmer over low heat till they turn golden brown in colour.
2. Stir in the flour and roast for a minute.
3. Then add the vegetable stock.
4. Add the bay leaf and salt and cook, covered, over low heat for 20 minutes.
5. Remove. Preheat the oven.
6. Cut the bread slices into small cubes.
7. Arrange the cubes in a bowl and pour the onion soup over them.
8. Top with the grated cheese.
9. Grill for 15 minutes or till the cheese melts. Serve hot.