Description
French Onion Lasagna is a decadent twist on the classic Italian dish, combining caramelized onions with a rich béchamel and gruyere cheese sauce, layered with tender lasagna noodles and crispy sourdough croutons for added texture. This comforting and savory casserole serves up the flavors of French onion soup in a hearty baked pasta format perfect for gatherings or family dinners.
Ingredients
Scale
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, to taste
- Freshly cracked black pepper, to taste
Sauce (Béchamel)
- 1/4 cup butter
- 1/4 cup flour
- 4 cups whole milk
- 2 cups gruyere cheese, grated
- Kosher salt, to taste
- Freshly cracked black pepper, to taste
Filling (French Onion)
- 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, to taste
- Freshly cracked black pepper, to taste
Instructions
- Preheat Oven: Preheat the oven to 375°F and prepare a 10×14 lasagna pan or 9×13 casserole dish for assembling the lasagna.
- Prepare Croutons: Toss the cubed sourdough bread with olive oil, granulated garlic, salt, and pepper in a bowl. Spread the bread cubes in a single layer on a sheet tray and bake in the preheated oven for 20 minutes or until golden and crispy.
- Cook Lasagna Noodles: Bring a large pot of salted water to a boil and cook the lasagna noodles according to package instructions until al dente. Drain and rinse in cold water to stop cooking, then set aside.
- Make French Onion Filling: In a large pan, melt the butter over medium-low heat and caramelize the sliced onions until camel-colored, about 20-30 minutes. Stir in the flour to coat the onions, then gradually add beef stock along with fresh thyme, balsamic vinegar, and Worcestershire sauce. Cook until the mixture thickens like gravy. Season with salt and pepper to taste and remove from heat.
- Prepare Béchamel Sauce: In a pot over medium-high heat, melt butter and stir in flour, toasting the roux for 30 seconds while stirring constantly. Slowly whisk in the whole milk, bringing the mixture to a boil while whisking to avoid lumps. Once thick enough to coat the back of a spoon, reduce the heat to low and stir in grated gruyere cheese until smooth and melted. Season with salt and pepper. Use an immersion blender if necessary to smooth the sauce.
- Assemble Lasagna: Spoon a layer of the onion filling on the bottom of the prepared pan. Shingle a layer of lasagna noodles over the filling. Spread one-third of the remaining onion filling evenly over the noodles, then sprinkle one-third of the baked croutons on top. Drizzle with béchamel sauce and sprinkle some mozzarella cheese. Repeat this layering process two more times, finishing with a layer of béchamel and gruyere cheese on top.
- Bake: Place the assembled lasagna in the preheated oven and bake for 40 minutes or until the top cheese is bubbly and golden brown.
- Rest and Serve: Allow the lasagna to cool for at least 10 minutes before slicing to set the layers and make for easier serving. Enjoy warm.
Notes
- Use day-old sourdough bread for the croutons to achieve the best crispiness.
- Caramelizing onions slowly is key for deep flavor; do not rush this step.
- For a vegetarian version, substitute the beef stock with vegetable stock and omit Worcestershire sauce or use a vegetarian alternative.
- The béchamel can be made smoother by using an immersion blender if lumps occur.
- Letting the lasagna rest after baking helps the layers to set and prevents it from falling apart.
- Leftovers can be refrigerated for up to 3 days and reheated gently in the oven.
Nutrition
- Serving Size: 1 slice
- Calories: 450 kcal
- Sugar: 6 g
- Sodium: 550 mg
- Fat: 22 g
- Saturated Fat: 13 g
- Unsaturated Fat: 7 g
- Trans Fat: 0 g
- Carbohydrates: 45 g
- Fiber: 3 g
- Protein: 18 g
- Cholesterol: 60 mg
