1 12-ounce package jumbo pasta shells
1 pound sweet Italian sausage, casings removed
1 Tbsp minced garlic
1 large egg
16-ounces ricotta cheese
10-ounces chopped frozen spinach, thawed, squeezed dry, chopped further (or 10 ounces chopped fresh spinach)
1 Tbsp chopped fresh basil or 1 teaspoon dried basil
1/4 cup unseasoned bread crumbs
1/2 teaspoon salt
1/2 teaspoon ground black pepper
Jar of tomato sauce
Bring a large pot of salted water to a boil (1 teaspoon salt per quart of water). Cook the pasta shells according to the instructions on the package. Drain, rinse in cold water, and set aside.
Add the sausage to the pan, breaking up the sausage into smaller bits. Cook sausage until cooked through and no pink remains, about 5 minutes. Add the garlic and cook until fragrant, about 30 seconds to a minute more. Remove pan from heat.
Beat the egg lightly in a large bowl. Mix in the ricotta, chopped spinach, basil, bread crumbs, salt, pepper, and sausage mixture. Fill each cooked pasta shell with some of the ricotta, spinach, sausage mixture.
Spread 1/2 cup tomato sauce over the bottom of the baking dish. Arrange the stuffed pasta shells in the dishes. Spread the remaining sauce over the top of the pasta shells.
At this point you can make ahead, to freeze (up to four months) or refrigerate before cooking. (If freezing, cover with foil, then wrap with plastic wrap).
Heat oven to 375°F; bake for 40 minutes, until bubbly.