Preheat the oven to 350ºF.

Bring a large pot of water to a boil, then salt generously. Add the pasta and cook according to package directions. Drain.

Meanwhile, heat the oil in a large skillet over medium heat. Add the sausage and cook until browned on both sides. Remove the sausage from the pan to a plate and cover lightly with foil. Reserve about 1 tablespoon of oil in the pan and drain the remainder. Return the pan to the heat and add the onion, zucchini and carrots. Cook, stirring often, until softened, about 5 minutes. Add the garlic and cook until fragrant, another 30 seconds.

Stir the spaghetti sauce and the undrained tomatoes into the vegetables. Bring to a boil, then reduce the heat. Simmer, uncovered, for 15 minutes.

In a small bowl, combine the egg and the ricotta cheese.

Spray 2 9x13-inch baking dishes with nonstick cooking spray. (Make sure one is freezer safe. I like to use a disposable aluminum pan.)

In each of the pans, layer one fourth of each of the drained pasta, the tomato sauce, the sausage, the ricotta mixture, cheddar cheese, and then the mozzarella cheese. Repeat the layers.

Cover the casserole that you are going to eat with foil, and bake for 15 minutes. Remove the foil and cook an additional 15 minutes, until heated through and the cheese is melted. Top with sliced green onions before serving.

Let the second casserole cool completely, the place a piece of plastic wrap over the top. Cover tightly with foil and freeze.

When ready to bake, allow the casserole to unthaw in the refrigerator for 24 hours. Remove from the refrigerator 30 minutes before baking. Carefully remove the foil and discard the plastic wrap. Recover the casserole with the foil and bake at 350º for 45 minutes, then remove the foil and bake an additional 10-15 minutes.