Adapted from recipes by Thomas Keller and Dorie Greenspan
4 pounds yellow onions
2 tablespoons butter
2 tablespoons olive oil
3-4 cloves of garlic, minced
1 tablespoon flour
1 cup vermouth (or dry white wine)
8 cups chicken broth
Freshly grated black pepper to taste
1/4 cup Cognac
1 1/2 cups grated Swiss cheese (Comté or Emmenthal preferred)
Baguette, cut into 1/2 inch slices
Olive oil and kosher salt to toast baguette
Peel onions, then cut in half through the root. Cut each half into thin slices. In Dutch oven, heat olive oil and butter. Add onions, garlic and sprinkle with Kosher salt. Slowly cook, over low heat, stirring frequently till onions start to caramelize. Do not allow to burn, but continue cooking till onions are really browned.
When onions are caramelized, add flour and cook for a minute or two. Add vermouth and reduce liquid by about half. Add chicken broth, and bring to boil. Reduce heat and allow soup to simmer at least 30 minutes. Add cognac and stir. Check for seasoning, adding black pepper and more salt to taste if needed.
Prepare croutons by brushing with olive oil and a sprinkle of Kosher salt. Broil till lightly toasted. Flip, brush with olive oil, and broil backside. Set aside.
Fill heat proof bowls with soup, leaving room to top with crouton. Place crouton over soup and put about 1/4 cup grated cheese over toasts. Put bowls on sheet pan and place under broiler. Broil till cheese is melted, bubbly and lightly brown. Serve immediately.