Best Vegetarian Spinach and Mushroom Lasagna Recipe

Ingredients

• 2 tablespoons olive oil or butter
• 1 medium onion, finely chopped
• 3 cloves garlic, minced
• 12 ounces mushrooms, sliced (340g)
• 10 ounces fresh spinach (280g)
• 1 teaspoon dried thyme or Italian seasoning
• Salt
• black pepper
• 4 tablespoons unsalted butter (60g)
• 1/4 cup all-purpose flour (30g)
• 4 cups milk (1 liter)
• 1/4 teaspoon ground nutmeg (optional)
• 9-12 lasagna noodles
• 2 cups shredded mozzarella cheese (200g)
• 1/2 cup grated Parmesan cheese (50g)