Ingredients

Béchamel Sauce:

• 5 tablespoons unsalted butter
• 5 tablespoons all-purpose flour
• 4 cups homogenized milk
• pinch nutmeg
• salt and pepper

Lasagna:

• 1/4 cup unsalted butter , divided
• 1 small onion , chopped
• 1 clove garlic , minced
• 1 carrot , peeled and finely diced
• 1 celery stalk , finely diced
• 1 (227 g) pkg cremini mushrooms , cut in 1/4-inch slices
• 1 (100 g) pkg oyster mushroom , coarsely chopped
• salt and pepper
• 500 g ground chicken (or ground turkey)
• 1 tablespoon all-purpose flour
• 2 cups chicken broth
• 1 teaspoon herbes de Provence
• 1 bay leaf
• 2 cups coarsely chopped spinach
• 375 g oven-ready lasagna noodles
• 2 cups grated Gruyere cheese
• 2 cups shredded mozzarella cheese