Bring a pot of water to a boil for the shells. Cook according to package directions; drain.
Meanwhile, in a large skillet, heat the olive oil over medium-high heat. Add onion and garlic and cook until onion is tender and beginning to brown, about 3 minutes.
Add turkey, salt, and pepper, and cook until meat is light golden and heated through, stirring occasionally.
Add artichoke hearts and stir to combine. Remove from heat; allow to cool.
In a large bowl, combine the cooled turkey mixture with ricotta cheese, Parmesan cheese, eggs, basil, parsley, salt, and pepper. Stir.
Cover the bottom of a 9x13-inch baking dish with 1 cup of marinara sauce. Holding a shell in the palm of your hand, stuff with large spoonfuls of turkey mixture, about 2 tablespoons per shell. Place each shell in the baking dish. Keep working until dish is full; you should have about 24 shells.
Drizzle remaining marinara sauce over shells and top with grated mozzarella.
Bake shells until warmed through and until cheese begins to brown, about 25 minutes.