Mince the onions. Saute the onions in butter until brown, but don't burn them.
Sprinkle on the flour and stir a few times, to form a roux.
Put 2 quarts of beef stock in a soup kettle. Add the salt & pepper and the bouquet garni. Cook over low heat for 40 minutes, discard the bouquet garni.
Cut the bread into very thin slices and lightly dry them in the oven (don't burn them). Put the bread in ovenproof bowls.
After tasting the stock and adjusting the salt and pepper, pour the stock over the bread. Cover the surface with cheese.
Set the soup bowls on a baking tray in a 450-degree oven and cook until the cheese is melted and a golden color.
Bon Appetit!
