Coarsely chop the greens.
Wash the meat and bones and simmer gently for 2 1/2 hours with the greens, bouquet garni, peppercorns, a little salt and the water.
Let the soup cool down
Remove the meat, bones and vegetables. Strain the soup through a sieve lined with a wet muslin cloth, cool completely and degrease.
Peel the onions and the garlic clove. Cut the onions into very thin slices.
Rub a crock pot with the halved garlic clove.
Melt the butter in the saucepan, saute the onions in it at a low temperature until golden brown, pour in the soup and simmer gently for 1 hour.
Season the soup to taste with salt, pepper and white wine, pour the soup in portions into ovenproof soup bowls, top each with 3 slices of bread and sprinkle the cheese on the bread.
Bake the soup portions in the preheated oven for 15 minutes.
Then carefully remove and serve.