Wash dandelions and pick over carefully. Roll in cloth and pat dry. Put into a salad bowl and set in warm place. Cut bacon in small cubes, fry quickly and pour over dandelions. Put butter and cream into a skillet and melt over low heat. Beat eggs, add salt, pepper, sugar and vinegar, then mix with the slightly warm cream mixture. Cook over high heat until dressing is quite thick. Pour, very hot, over the dandelions, stir well and serve.