In a large flat bottomed pan melt the butter and add the thinely slice onions depending on the size of the pan you may which to do this batches. These onions need to be cooked until they are nicely golden and soft. At this point add the white wine and allow this to reduce until its got a nice thick consistency.
Add the chopped garlic and the bay leaf continue cooking for about 3 minutes. Now add the beef stock little my little till you have none left, you need to let the stock reduce each time or you will end up with a very thin soup. Be prepared for each time you add the stock for it to take a little longer.
Before serving add sugar, salt and pepper to taste. If you are using instant stocks be very careful adding the salt.
If you have a French stick (or similer) take a few diaginal cuts drizzle lightly with olive oil and grill both sides, and place this on top of the soup when serving. You may also want to consider adding a little strong cheese when grilling.