1. Pour boiling water over the unpeeled onions, let stand for a few minutes, then drain. Now peel the onions and trim off the root ends.
2. Place the onions in a large pan with the oil, sultanas, stock, vinegar, garlic, tomato puree and bouquet garni. Season to taste with salt and pepper.
3. Bring the contents of the pan to boil, then lower the heat, cover and simmer for 40-50 minutes until the onions are tender when pierced with a sharp knife.
4. Remove the bouquet garni and transfer to a serving dish. Serve hot or cold sprinkled with parsley.
For a stronger flavor, add 3 cloves, 5 pink peppercorns and a small piece of mace.