For the French Onion Soup:
1T Unsalted Butter
½lb Thick Cut Applewood Smoked Bacon, Cut into Lardons (reserve the rendered fat)
6-8lbs Yellow Onions, Thinly Sliced
¼C Sugar (plus a little extra to sweeten the soup if needed)
Smoked Fleur de Sel + Fresh Cracked Pepper
2 Sprigs of Fresh Thyme
1/3C Cognac (sherry may be substituted)
1-2T Aged Balsamic Vinegar (optional)
1C Red Wine
4C Unsalted Beef Stock (preferably homemade, but store-bought is fine)
Slices of Sourdough Bread (make sure it is able to fit inside the bowl)
Rendered Bacon Fat, For Frying the Bread
½lb Gruyere Cheese, Grated
½lb Aged Cheddar Cheese, Grated
Freshly Grated Parmesan Cheese (to top the other cheeses)
Crispy Bacon Lardons, For Garnishing (made crispy in the first step)
Fresh Parsley or Chives, Minced (for garnishing)
1. Beginning the Soup: Use a large soup pot that will hold all of the onions and liquid. Place the pot over medium heat and melt the 1T of butter. Add the bacon lardons and cook until the bacon has rendered all of its fat and it is crispy. Strain the bacon from the pot into a small bowl and set it aside until the soup is finished. Add all of the thinly sliced onions; sprinkle them with 2t smoked fleur de sel, some fresh cracked pepper, and the sugar. Stir to combine. Cover and cook until the onions have heated through and started to steam, about 30-45 minutes.
2. Caramelizing the Onions: Uncover the pot, reduce the heat to low, add in the fresh thyme, and cook, stirring continuously (you should be able to leave the onions alone for an hour once they’ve released their water). I kept cooking my onions for at least 3-4 hours, low + slow until they reach a deep, dark golden brown.
3. Making the Bacon Fat Fried Sourdough Slices: In a sauté pan, over medium heat, melt some bacon fat and fry the slices of sourdough bread until they are golden brown and toasty. Preheat the oven to 200 degrees. Place the slices of fried bread onto a baking sheet and keep them warm until you are ready to top the soup with them.
4. Finishing the Soup: When the onions have completely cooked down and all their liquid had cooked out, add in the cognac, balsamic, red wine, beef stock, and water. Raise the heat to high and bring the soup to a simmer, and then reduce the heat to low. Taste and season with smoked fleur de sel, fresh cracked pepper, and some sugar if needed. If the soup is too sweet, you can add an extra tablespoon of balsamic. If you want the soup to have more depth, add a little more red wine (shhh, no one has to know).
5. Serving the Soup: Preheat the broiler of your oven. Portion the soup into the bowls, top with a bacon fat fried slice of sourdough bread, cover with a handful of gruyere cheese and a handful of aged cheddar cheese, and finish with a mound of freshly grated parmesan. Broil until the cheese is melted and nicely browned. Garnish the top with crispy bacon lardons and minced herbs. Serve immediately.