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French Onion Lasagna Recipe

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4.2 from 59 reviews

This French Onion Lasagna is a decadent twist on the classic lasagna, layered with caramelized onions infused with thyme, Worcestershire, and balsamic vinegar, a creamy Gruyere béchamel sauce, crunchy garlic-infused croutons, and tender lasagna noodles. It’s baked to golden perfection, combining rich French onion soup flavors with comforting Italian pasta layers for a unique and indulgent casserole perfect for cozy dinners.

Ingredients

For the Lasagna:

  • 1 lb. lasagna noodles, cooked
  • 8 oz. mozzarella cheese, grated
  • 6 cups sourdough bread, cubed
  • 1/4 cup olive oil
  • 1 teaspoon granulated garlic
  • Kosher salt and freshly cracked black pepper, to taste

For the Sauce (Béchamel):

  • 1/4 cup butter
  • 1/4 cup flour
  • 4 cups whole milk
  • 2 cups Gruyere cheese, grated

For the Filling (Caramelized Onion Mixture):

  • 1/4 cup butter
  • 1/4 cup all-purpose flour
  • 3 yellow onions, sliced
  • 3 tablespoons unsalted butter
  • 2 teaspoons fresh thyme
  • 1 teaspoon Worcestershire sauce
  • 1 tablespoon balsamic vinegar
  • 1 quart good beef stock
  • Kosher salt and freshly cracked black pepper, to taste

Instructions

  1. Preheat the Oven: Set your oven to 375°F (190°C) and prepare a 10×14 inch lasagna pan or a 9×13 inch casserole dish by greasing it lightly or setting it aside.
  2. Prepare Garlic Croutons: Toss cubed sourdough bread with olive oil and granulated garlic. Spread evenly on a sheet tray, season with kosher salt and freshly ground black pepper, and bake in the preheated oven for 16 to 20 minutes, until golden and crisp. Remove and set aside.
  3. Cook Lasagna Noodles: Bring a large pot of salted water to a boil. Cook the lasagna noodles according to package instructions until al dente. Drain and rinse with cold water to stop cooking, then set aside separated.
  4. Caramelize Onions for Filling: In a large pan over medium-low heat, melt 3 tablespoons unsalted butter. Add sliced yellow onions and cook slowly, stirring occasionally until onions turn golden camel color, releasing their natural sweetness.
  5. Make Onion Filling Base: Stir in 1/4 cup all-purpose flour to the caramelized onions until combined well. Gradually add beef stock, fresh thyme, Worcestershire sauce, and balsamic vinegar. Cook while stirring gently until the mixture thickens to a gravy consistency. Season with salt and freshly cracked black pepper to taste, then remove from heat and set aside.
  6. Prepare Béchamel Sauce: Melt 1/4 cup butter in a pot over medium-high heat. Stir in 1/4 cup flour and cook the roux for 30 seconds, stirring constantly to avoid burning. Whisk in 4 cups whole milk slowly, continuing to whisk to break any lumps. Bring the mixture to a gentle boil until it thickens enough to coat the back of a spoon. Reduce heat to low, stir in 2 cups grated Gruyere cheese until melted and smooth. Season with salt and pepper. Use an immersion blender if necessary to achieve a smooth texture.
  7. Assemble Lasagna Layers: Spoon a layer of the onion filling into the bottom of the prepared pan. Arrange a layer of lasagna noodles on top in a shingled fashion. Spread about one-third of the onion filling evenly over the noodles, then sprinkle one-third of the garlic croutons on top. Drizzle with a generous layer of béchamel sauce. Repeat this layering process two more times, ending with béchamel sauce on top.
  8. Add Final Cheese Topping and Bake: Sprinkle the top of the assembled lasagna with grated Gruyere cheese and shredded mozzarella cheese. Place in the oven and bake for 35 to 40 minutes until the cheese topping is melted, bubbly, and golden brown.
  9. Cool and Serve: Remove lasagna from the oven and allow it to cool for at least 10 minutes to set. Slice into portions and serve warm, enjoying the rich layers of French onion flavor and creamy textures.

Notes

  • Use good quality beef stock for the best flavor depth in the onion filling.
  • If you prefer a vegetarian version, substitute beef stock with vegetable stock and omit Worcestershire sauce or use a vegetarian alternative.
  • Make sure to slowly caramelize onions on low heat to develop deep sweetness without burning.
  • The garlic croutons add a delightful texture contrast; ensure they are baked until crisp but not overly browned.
  • Use an immersion blender for béchamel sauce if you notice any lumps for a silky smooth sauce.
  • Allowing the lasagna to rest before slicing helps maintain clean, neat slices.
  • This dish can be made a day ahead and reheated covered at 350°F for 20-25 minutes.

Find it online: https://flavorspath.com/french-onion-lasagna-recipe/