french onion soup, Luxembourg version

Since doing a recipe base for bistro we are at now, wanted to add the one we used in nyc at lux. Its similar, bit deeper color with the added flour and sugar. In fact, the sugar can be cut in half if you cook the onions right. You won't need it all. 2 case thinly sliced onions. 4lb fresh butter, unsalted. 1 bunch thyme. 1 sprig Rosemary. 4 fresh bay leaves. 2TB black peppercorns. 7 and 1/2 gallons veal stock. 1 and 1/2 gallon light chicken stock. 2 cups salt. 1 cup sugar. 1/4 cup sherry vinegar. 1/2 cup flour. Melt butter in large rondo. Add onions, salt, pepper, and sugar. Cook for hours until very soft and caramelized. Season. Add bouquet garni of thyme, rosemary, peppercorns and bayaves. Add sherry vinegar. Reduce. Add wine and reduce. Add flour and cook 10 minutes until absorbed. Add veal broth and chicken stock. Season. Simmer another 3 hours and gently season again. For service: laddle soup into cups, oven proof. Croutons, gruyer and parmesan. Broil until cheese is nicely browned.