Marsala wine is the secret to this deliciously easy French onion soup. Caramelized onions, in a rich beef broth seasoned with thyme and topped with croutons and melted cheese. A perfect comfort food for cold days!
Bring beef broth to a boil in a large pot. Add sugar and malt vinegar. Reduce heat and simmer for 5 minutes.
Meanwhile, in a skillet over medium-high heat, sauté onions and thyme in butter until caramelized, about 3-5minutes. Scoop out onions and add to pot of beef broth. Deglaze the skillet by adding Marsala wine; bring to a boil and then scrape the sides. Carefully pour wine with flavorful onion bits into the pot of broth. Finally, season broth with salt and pepper to taste.
Ladle soup into oven-safe bowls or ramekins and place a handful of croutons in each. Sprinkle on Parmesan and Swiss cheese then layer 2 slices of provolone on top.
Place bowls on a cookie sheet and broil on low in a preheated oven until cheese bubbles and turns golden brown. About 5-7 minutes.
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Notes
For added flavor be sure onions are caramelized but not burnt. Adjust heat as needed. Onions should be translucent with a light caramel brown color when done.Add fresh or dried thyme in with butter and onions to bring out the most flavor of this herb.You can skip the step of deglazing the onion skillet and add the Marsala wine directly to the broth, however, you'll miss out on some good flavor!