Mix well-drained, cooked spinach with ricotta, shredded mozzarella, grated Parmesan, an egg, minced garlic, salt, pepper, and chopped fresh basil or parsley. Fill cooked jumbo shells and nestle them into a baking dish spread with marinara.
Cover with more sauce and cheese, then bake at 375°F (190°C) until heated through and bubbly, about 20–25 minutes. Let rest briefly before serving.
Make it heartier:
This dish is easy to scale and reheats well for leftovers.