Vegetable and Sausage Sauce
- In a food processor, finely chop the mushrooms. Transfer to a bowl. Finely chop the remaining vegetables. Set aside with the mushrooms.
- In a pot over medium-high heat, brown the sausage meat in the oil while breaking it up with a wooden spoon. Add the vegetable mixture and cook for 5 minutes, stirring often. Add the remaining ingredients. Season with salt and pepper. Bring to a boil and simmer for 40 minutes.
- Meanwhile, in another pot over medium heat, melt the butter. Add the flour and cook for 1 minute while stirring with a whisk. Add the milk while whisking. Bring to a boil. Simmer gently for 2 minutes or until thickened. Add the cheese and stir until completely melted. Season with salt and pepper. Cover and keep warm.
- With the rack in the middle position, preheat the oven to 375°F (190°C).
- Cover the bottom of a 13 x 9-inch (33 x 23 cm) baking dish with 1 cup (250 ml) of the vegetable sauce. Cover with a layer of lasagna noodles and half of the béchamel. Cover with another layer of noodles and 2 cups (500 ml) of the vegetable sauce. Continue layering the remaining béchamel sauce, noodles and vegetable sauce for a total of 4 layers. You can freeze at this stage, if desired. Top with the mozzarella. Place the baking dish on a baking sheet.
- Bake for 40 minutes. Brown the top under the broiler, if desired. Let sit for 15 minutes before serving.