This cheesy French onion soup casserole belongs on your dinner table this Fall.

french onion soup casserole

Everyone loves French onion soup, right?  A rich oniony broth, a hunk of broth-soaked bread, and cheese on top?  What’s not to love?  Well, for vegetarians the answer is easy: beef broth.  French onion soup is almost always made with beef broth, so it’s really frustrating when that’s the “vegetarian” option on menus.

I’ve been making my own vegetarian version for years and lately I’ve been seeing French onions soup casseroles popping up on Pinterest.  They always look tempting, so I decided to turn my soup into a vegetarian version of the casserole.  (Side note: I can’t exaggerate the rage I feel when these other posts use beef broth and then talk about how the recipe is a great vegetarian dish.  RAGE STROKE!!!!)

The biggest change I made (other than mushroom broth instead of beef broth) was that I put the bread in the dish first.  I don’t understand why all the other casseroles out there have the bread on top.  Isn’t the whole point of the bread to sop up some broth and take on its flavor?

This turned out really tasty.  I definitely wouldn’t serve it as a main course, but it was a great bread alternative.  Filling and comforting.  What more could I want from an autumn side dish?

French Onion Soup Casserole

  • 6 large onions, sliced thin
  • Three tablespoons olive oil
  • One tablespoon butter
  • Four leaves of fresh sage, minced
  • Five or six sprigs of fresh thyme, stripped
  • 1 cup chopped crimini (Baby Bella) mushrooms
  • 1/3 cup fresh parsley, minced
  • 1/2 cup Marsala wine
  • About 1 cup mushroom broth
  • One loaf of Italian or French bread
  • Swiss cheese

Preheat oven to 350° F.  In a large pot, saute the onions in the olive oil and butter over medium-low heat until they start to soften.

onions in pan

Add the mushrooms, herbs, and wine, lower heat to low, and slowly cook until the onions reach your desired level of caramelization.  Stir occasionally and when the onions start to dry out add mushroom broth.  You want this a little loose and soupy so that there will be plenty of juice for the bread to soak up!

caramelized onionsWhile the onions are cooking, slice your bread into thick (1/2″) slices.  Toast the bread.  Line a greased 11″x9″ pan with the toast.

Cover the toast with the onion/mushroom mix.

french onions soup casserole caramelized onions

Add the cheese.  If you have shredded cheese, that’s great.  I happened to have sliced cheese and that’s fine too.

french onion soup casserole caramelized onionsBake until the cheese melts and starts to turn golden, about fifteen minutes.

french onion casserole 3Enjoy!

french onion soup casserole

Looking for a great, warming side dish this fall or winter?  Try this French onion soup casserole!  All the flavors you love from French onion soup!