There is a tremendous amount of variations in onion soup recipes.   Since the recipe for this soup has only three main ingredients, onions,  broth, and cheese croutons, each part needs to be carefully done.  The recipe below is the one I found that works for me.  The stock has a rich taste and only a little salt.   Yellow onions were the perfect ones for the caramelization, and since we keep our cheese intake low the cheese croutons were perfect for us.  

Ingredients - Beef Stock:

2 pounds beef necks
3 carrots, roughly chopped
3 celery stalks, roughly chopped
1 onion, roughly chopped
4 garlic cloves, cut into two or three pieces
1/4 cup black peppercorns

1 bunch thyme
1sprig rosemary
1 bay leaves
2 cups red wine
2 Tablespoon tomato paste

Directions - Beef Stock

Preheat the oven to 500°F. Place the bones on a roasting pan for 45 minutes. Then, add the celery, carrots, onions, garlic, peppercorns, thyme, rosemary, and bay leaves, and roast for another 20 minutes. Deglaze the pan with a little of the red wine and add the tomato paste. Place the ingredients into your stockpot, including the rest of the red wine and scraps from the bottom of the pan. Add 4 quarts of water, bring to a boil, and let your stock simmer  on medium heat for 5–6 hours, I put on the lid, slightly opened.

Ingredients - French Onion Soup

1 Tablespoon Olive Oil
1 Tablespoon butter
1 pound yellow onions
1 clove garlic

1/4 cup red wine
4 cups beef stock
fresh thyme
salt and pepper to taste

Directions - French Onion Soup

1.  Thinly sliced onions.
2.  Add oil and butter - sauté in moderate heat about 30 40 minutes.
3.  Add minced garlic and sauté another minute.
4.  Add wine to deglaze.
5.  Add stock, simmer for 35 minutes.  Taste, then add salt and pepper as desired.

Croutons and Cheese

Toast a favorite substantial bread.  Cover with your favorite cheese, gruyere is often recommended and microwave for 15 seconds.  Cut the toast into crouton pieces and place on soup.  Enjoy!