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A serving of caramelized onion and mushroom lasagna with gruyere thyme cream sauce.

Caramelized Onion And Mushroom Lasagna With Gruyère Thyme Cream Sauce

AndreeaB
This Caramelized Onion and Mushroom Lasagna with Gruyère Thyme Cream Sauce is rich, cheesy, and deeply flavorful — all the comfort of classic lasagna, but with a creamy white sauce instead of tomato and layers of golden onions, mushrooms, and nutty Gruyère.
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Prep Time 1 hour
Cook Time 50 minutes
Total Time 1 hour 50 minutes
Course Main Course
Cuisine French-Italian
Servings 8 servings
Calories 470 kcal

Ingredients
  

For the filling

  • 3 large onions, thinly sliced
  • 2 tbsp butter
  • 1 tbsp olive oil
  • 1 lb mushrooms (cremini, baby bella, or shiitake), sliced
  • 2 cloves garlic, minced
  • 2 tsp fresh thyme leaves (or 1 tsp dried)
  • 1 cup shredded Gruyère cheese
  • 1 cup ricotta cheese
  • Salt and pepper to taste

For the sauce (creamy thyme béchamel)

  • 3 tbsp butter
  • 3 tbsp all-purpose flour
  • 3 cups whole milk
  • 1 tsp Dijon mustard
  • ½ tsp nutmeg
  • ½ cup grated Parmesan
  • salt & pepper to taste

For layering

  • 9-12 lasagna noodles
  • 1 cup shredded mozzarella for topping

Instructions
 

Caramelize onions:

  • In a large skillet, cook onions in butter and olive oil over medium heat for 25–30 minutes, stirring often until deep golden.
    3 large onions, thinly sliced , 2 tbsp butter, 1 tbsp olive oil

Sauté mushrooms:

  • Add mushrooms, garlic, and thyme. Cook until mushrooms are browned and any liquid evaporates. Season with salt and pepper.
    1 lb mushrooms (cremini, baby bella, or shiitake), sliced, 2 cloves garlic, minced, 2 tsp fresh thyme leaves (or 1 tsp dried), salt & pepper to taste

Make the béchamel:

  • Melt butter in a saucepan, whisk in flour, then slowly add milk. Stir until smooth and thickened. Add Dijon, nutmeg, Parmesan, salt, and pepper.
    3 tbsp butter, 3 tbsp all-purpose flour, 3 cups whole milk, 1 tsp Dijon mustard, ½ tsp nutmeg, ½ cup grated Parmesan, Salt and pepper to taste

Mix the filling:

  • Combine ricotta, half of the Gruyère, and half of the onion-mushroom mixture.
    1 cup ricotta cheese, 1 cup shredded Gruyère cheese

Assemble:

  • Layer noodles → ricotta mixture → béchamel → a few spoonfuls of caramelized onions and mushrooms → repeat.
    9-12 lasagna noodles
  • Finish with béchamel and top with remaining Gruyère and mozzarella.
    1 cup shredded mozzarella for topping

Bake:

  • Cover and bake at 375°F (190°C) for 30 minutes. Uncover and bake 10–15 more until golden and bubbly.

Rest:

  • Let it sit 10 minutes before slicing. Garnish with fresh thyme.

Nutrition

Serving: 314gCalories: 470kcalCarbohydrates: 38gProtein: 22gFat: 25gSaturated Fat: 15gSodium: 800mgFiber: 3gSugar: 8g
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