Quart vegetable stock
Teaspoon lemon juice (equivalent in substitute)
1) Preheat oven to 200°C. If using fresh chestnuts, use a sharp knife to cut a cross into the flat side of the chestnuts. Transfer to a baking tray and bake for about 30 minutes, until chestnuts feel quite soft. Set aside until cool enough to handle (they peel much better when warm), then use a small knife to remove the shells and any furry skins.
2) Heat margarine in a large saucepan. Add the onion and cook over low heat for 5-6 minutes until the onion softens and the mixture just starts to turn golden. Add chestnuts, stock and sugar. Season, then bring to the boil. Reduce heat to low and simmer, partially covered, for 45 minutes.
3) When warm enough, stir in the lemon juice and serve.