Cheesy Sausage and Vegetable Lasagna

Make the sausage-vegetable tomato sauce: heat olive oil in a large heavy-bottomed casserole or Dutch oven over low heat. Sauté onions, carrots, and celery, stirring occasionally, for about 5 to7 minutes.

Add pork sausage. Cook for about 5 minutes, stirring frequently to break up lumps. Add mushrooms and cook for 1 minute. Add eggplant and zucchini; cook until tender, about 2 minutes.

Add diced tomatoes, tomato purée, tomato paste, stock, oregano, and parsley. Stir to mix and bring to a boil.

Reduce heat and let mixture simmer for about 30 minutes, stirring once in a while. Add more stock, if needed. Season to taste with salt and pepper.

Make the béchamel sauce: melt butter in a medium saucepan. Add flour and cook for 2 minutes.

Gradually add warm milk, mixing continuously with a whisk until smooth. Let mixture boil and thicken a little. Season with salt, nutmeg, and pepper.

Preheat oven to 350°F.

To assemble, spread about a third of the sausage-vegetable sauce on the bottom of a deep 9x13-inch baking dish. Pour about 3/4 to 1 cup of the béchamel sauce over. Arrange 4 sheets of cooked lasagna noodles over the sauce. Repeat layering 2 more times. Cover top with remaining béchamel sauce then sprinkle evenly with ricotta, if using, and grated mozzarella cheeses.

Bake in the oven for 50 minutes to 1 hour, or until the pasta feels tender when pierced with a skewer. Let lasagna rest for 10 minutes before serving.