5 Pounds total for onions total, see the ratio I use below:
4 Large yellow onions
2 Large sweet onions
6 Tablespoons salted butter, I like Tillamook.
2 Sprigs of fresh thyme
2 Bay leaves
¾ cups dry white wine, such as Chardonnay or Viognier
4 Cups of beef broth, high quality is key
1.5 Cups chicken broth
1 Teaspoon Worcestershire sauce
Salt/Pepper, to taste
3 Tablespoons olive oil (optional)
6 slices Gruyere cheese see below for substitution options
Each type of onion adds a different element of flavor. Combining the two allows you to enjoy the best of what each has to offer.
Slice the onions into strings of medium-size. They'll shrink down and you don't want them too thin.
Melt the butter in a large (4-5 quart) soup pot or dutch oven over medium-low or low heat. Wait until it begins to foam, this allows water to evaporate out, leaving the butter more clarified and smooth.
Add the onions and use tongs to toss and coat them in the butter. Leave them uncovered as they cook.
The onions will caramelize slowly, this takes patience. 6 large onions could take over an hour to fully caramelize, at medium-low heat. Stir the onions every 15 minutes. During the last 15 minutes, increase the heat to medium-high and toss more frequently. They are done when they are richly brown and sweet.
The onions will caramelize slowly, this takes patience. 6 large onions could take over about 10 hours to fully caramelize, at low heat. Stir the onions every so often. During the last 15 minutes, increase the heat to medium-high and toss more frequently. They are done when they are richly brown and sweet.
Decrease heat to medium, add the white wine and cook for an additional 2-3 minutes. Use a silicone spatula to "clean" (deglaze) the bottom of the pot with the wine.
Add the beef broth, chicken broth, Worcestershire sauce, bay leaves, and thyme. Simmer for another 45 minutes, with the lid cracked.
You are ready to go... Just add cheese and bread.