1. Preheat the oven to 350°F/180°C (Gas Mark 4).
1. Cook the chestnuts with a little water and yeast extract, for 15 minutes.
2. In a pan cook the onions until golden and add the sage.
3. In a pie dish layer the onions, chestnut and tomato slices on top of each other.
4. Spread the bread crumbs on top, dot with margarine and bake for 30 minutes.
5. Serve hot with sour dough bread, green vegetables or a crisp salad.