This French Onion Soup Casserole Will Make Your Mouth Water

french onion gratin soup

Croissants. Beef Bourguignon. Crème brûlée. Ratatouille. Chocolate soufflé. Baguettes. Crepes. And for some reason, escargot. French culture has had an enormous impact on the world’s palate, most of it good, and one of the most famous staples is French Onion Soup. But have you ever had it in casserole form? This French Onion Soup Casserole will make your mouth water. One taste and, well, you’ll want to be the judge.


  • 3 medium sweet onions, sliced
  • 3 tablespoons butter
  • 4 cups beef broth
  • 1 teaspoon Worcestershire sauce
  • oz French baguette bread, sliced about ½-inch in thickness (approximately 10-12 small slices)
  • 1 cup (4 ounces) shredded mozzarella cheese
  • ¼ cup grated Parmesan cheese

Directions For Making French Onion Soup Casserole

  • In a large saucepan, melt butter over low heat.
  • Add onions and cover. Cook for approximately 30 minutes, occasionally stirring.
  • Add beef broth and Worcestershire sauce and heat the mixture until boiling.
  • After it boils, reduce the temperature to low and allow it to simmer uncovered for approximately 30 minutes so the broth reduces.
  • In a medium greased casserole dish, pour your onion and broth mixture.
  • Place lightly toasted slices of bread in a single layer on top of the mixture.
  • Cover the bread with a thick layer of the shredded mozzarella and add grated Parmesan on top.
  • Set your oven for 350 and bake uncovered for 20-30 minutes or until the cheese is melted and brown on top.

You might also like: Power Up In The New 2023 RAV4

Tips And Tricks For Making Your Soup

  • Cooking the onion for a full half hour is worth every minute. It gives the casserole the rich flavor you want in a traditional French Onion Soup.
  • If you don’t have mozzarella you can use another cheese that is good for melting such as gruyere, fontina, or even white sharp cheddar.
  • Definitely use beef broth to give the casserole an authentic flavor.
  • You could consider adding more protein such as chicken or sausage if you want.

Disclaimer: The stock image is being used for illustrative purposes only, and it is not a direct representation of the business, recipe, or activity listed. Any person depicted in the stock image is a model.