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Extreme close-up of a serving of caramelized onion pasta bake on a fork, showing the creamy sauce and melted cheese.

French Onion Pasta Bake: The Ultimate Comfort Food Casserole

This French Onion Pasta Bake transforms the classic soup into a hearty casserole with deeply caramelized onions, savory beef broth, tender pasta, and a bubbly, golden-brown Gruyère cheese crust. The ultimate comfort food dinner.
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Prep Time 15 minutes
Cook Time 1 hour 15 minutes
Total Time 1 hour 30 minutes
Servings: 8 servings
Course: Dinner, Main Course
Cuisine: American, French
Calories: 550
Ingredients Equipment Method Notes

Ingredients
  

  • 3 tbsp Unsalted Butter
  • 1 tbsp Olive Oil
  • 3 lbs Yellow Onions thinly sliced
  • 4 cloves Garlic minced
  • 1 tbsp Fresh Thyme Leaves
  • 3 tbsp All-Purpose Flour
  • 4 cups Beef Broth low-sodium
  • 1 tbsp Worcestershire Sauce
  • 1 lb Pasta such as rigatoni, penne, or ziti
  • 8 oz Gruyère Cheese shredded
  • 4 oz Mozzarella Cheese shredded
  • 0.5 cup Parmesan Cheese grated
  • 0.25 cup Breadcrumbs optional, for topping
  • Salt and Black Pepper to taste

Equipment

  • 1 Large Dutch oven or pot
  • 1 9x13 inch baking dish
  • 1 Large Pot (for pasta)

Method
 

  1. Preheat oven to 375°F (190°C).
  2. In a large Dutch oven over medium heat, melt butter and olive oil. Add sliced onions and a pinch of salt. Cook, stirring occasionally, for 45-50 minutes until deeply golden brown and caramelized.
  3. Stir in the minced garlic and fresh thyme, and cook for 1 minute more until fragrant.
  4. Sprinkle the flour over the onions and cook for 1 minute, stirring constantly.
  5. Gradually whisk in the beef broth and Worcestershire sauce. Bring to a simmer and cook for 5 minutes, allowing the sauce to thicken slightly. Season with salt and pepper to taste.
  6. Meanwhile, cook pasta in a large pot of salted water until 1-2 minutes shy of al dente. Drain well.
  7. Add the drained pasta to the Dutch oven with the French onion sauce. Stir until the pasta is fully coated.
  8. Transfer the mixture to a 9x13-inch baking dish. In a bowl, combine the shredded Gruyère, mozzarella, and grated Parmesan. Sprinkle the cheese mixture evenly over the pasta. Top with breadcrumbs, if using.
  9. Bake for 15-20 minutes, or until the sauce is bubbly and the cheese is melted and golden brown. Let it rest for a few minutes before serving.

Notes

For the best flavor, do not rush caramelizing the onions; this step is crucial for developing the deep, sweet flavor profile.
Shred your own cheese for the smoothest, meltiest topping.
Store leftovers in an airtight container in the refrigerator for up to 4 days.