1

Heat oven to 400° F. Cook the ziti according to the package directions. Meanwhile, heat the oil in a large pot over medium heat.

2

Add the onion, salt, and pepper and cook for 5 minutes. Add the beef and cook, crumbling it with a spoon, until no trace of pink remains, about 7 minutes.

3

Spoon off and discard any excess fat. Add the garlic and oregano (if using) and cook for 2 minutes. Add the pasta sauce and cook for 3 minutes.

4

Remove from heat. Add the drained ziti to the pot and toss. Add the ricotta, spinach, and 1/4 cup of the Parmesan and toss again.

5

Spread the mixture into a 9-by-13-inch baking dish. Sprinkle with the mozzarella and the remaining Parmesan. Bake until the mozzarella melts, about 15 minutes.

6

To freeze...

7

Assemble-but do not bake-the casserole. Cover tightly with two layers of aluminum foil. Store for up to 3 months.

8

To reheat...

9

Thaw overnight in the refrigerator or thaw partially in the microwave. Cover and heat in a 350° F oven for 1 hour. Uncover and heat until the mozzarella melts, about 10 minutes more.