Thinly slice the onions; you will have 5 to 6 cups.

In a large soup pot, over medium-low heat, melt the butter.

Add the onions and cook, stirring often, until limp and soft, about 20 minutes.

This makes the onions nice and sweet.

Turn up the heat to medium-high and cook the onions until golden brown, about 10 minutes. Do not burn.

Lower the heat to medium. Add the flour and cook for 2 minutes.

Add the vegetable stock, water, salt, wine, mustard, and bay leaf. Bring to a boil, stirring frequently.

Adjust the heat to a high simmer and cook (with the lid off) for 30 more minutes.

Taste and season with more salt and pepper, if needed.

At this point you may refrigerate or freeze the soup; otherwise, ladle the soup into individual broiler-proof bowls.

Bean bowls with handles are great.

Lightly lay a slice of French bread on the top of the soup. Do not push the bread down into the soup.

(Alternatively, you can cut up more than one slice of bread and fit it into the bowl to cover the soup.)

Lay the sliced non dairy mozzarella cheese over the bread completely, to keep the bread from burning.

Put the bowl or bowls on a cookie sheet (two at a time for safety).

Turn on the broiler and slide your cookie sheet under the oven broiler, on the top shelf.

Watch carefully— do not walk away.

Take out the pan when the cheese has lightly turned to a dark golden shade here and there.