Creamy French Onion Mushroom Rice Casserole Recipe


  • Rice: 2 cups long-grain white rice (jasmine or basmati are excellent)
  • Broth: 3 ½ cups chicken broth
  • Fat: 3 tablespoons unsalted butter
  • Aromatics: 1 large sweet onion, chopped
  • Mushrooms: 8 ounces white button mushrooms, thinly sliced
  • Seasonings: ¾ teaspoon dried thyme, ½ teaspoon sugar, ½ teaspoon black pepper, 1 bay leaf
  • The French Onion Touch: ½ cup beef broth, 1 tablespoon Worcestershire sauce, 3 cloves garlic, minced
  • Thickener: 5 teaspoons all-purpose flour (or gluten-free sweet rice flour)
  • Creamy Element: 2 cups milk (whole milk is best, but almond or other alternatives work)
  • Cheese: 6 ounces shredded Fontina cheese (or Gruyere, Swiss, or Provolone)


Prep and Preheat:

  • Preheat your oven to 375°F (190°C).
  • Grease a 9×13-inch baking dish.

Cook the rice:

  • Bring the 3 ½ cups of chicken broth to a boil. Add the rice, stir, then lower the heat to a simmer. Cook until the rice is al dente, approximately 15 minutes.
  • Once cooked, allow the rice to rest for 5 minutes, then fluff with a fork and set aside.

Sauté the veggies:

  • Melt the butter in a large skillet over medium heat. Add the onions and cook until softened, about 5 minutes.
  • Add the mushrooms and cook until they release their liquid and soften, about 5-7 minutes.

Flavor Explosion:

  • Add the beef broth, Worcestershire sauce, thyme, sugar, black pepper, and bay leaf to the skillet. Cook for a minute or two to meld flavors.
  • Stir in the garlic and cook until fragrant, about 30 seconds.

Make the Sauce:

  • Sprinkle the flour over the vegetables and cook for 1 minute, stirring constantly, to prevent clumping.
  • Slowly whisk in the milk. Bring to a gentle simmer, stirring constantly, until the sauce thickens.

Cheese Please:

  • Remove the sauce from the heat. Stir in half of the shredded Fontina cheese until melted.
  • Taste and adjust seasonings with salt and pepper if needed.


  • Gently fold the cooked rice into the creamy sauce mixture.
  • Pour the mixture into the prepared baking dish. Sprinkle the remaining Fontina cheese evenly over the top.

Bake and Enjoy!

  • Bake uncovered for 20-25 minutes, or until the cheese is melted, bubbly, and lightly browned.
  • Let the casserole rest for 5-10 minutes before serving. This allows the flavors to settle and makes it easier to cut.


  • Customize it: Add other veggies like bell peppers or spinach. Feel free to use a different type of cheese that melts well.
  • Make Ahead: Assemble the casserole up to a day in advance. Cover and refrigerate. Increase baking time by 10-15 minutes if baking straight from the fridge.
  • For added richness, substitute heavy cream for half of the milk.


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