Cook the pasta shells in a large pot of well-salted water until al dente. Drain and rinse.
Spread the creamed spinach in the bottom of the baking dish. Set aside.
In a mixing bowl, combine ricotta, mozzarella, Parmesan or Pecorino, black pepper, and lemon zest. Stir until well combined.
Fill the pasta shells with the cheese mixture and place in the baking dish.
Bake for 20-25 minutes until cheese is melted and bubbling around the edges.
Garnish with black pepper, parsley, and extra Parmesan or Pecorino cheese.
Cook the pasta until just al dente. This keeps the pasta firm enough so it's easy to fill. The shells will finish cooking in the oven for the perfect texture.
Store leftovers in an airtight container in the refrigerator for up to three days. To reheat, cover an oven-safe dish with aluminum foil and bake at 375 degrees until warmed through.
Uncooked stuffed shells can be stored, tightly covered, in the refrigerator for up to 3 days. Prepare as directed up to the point of baking. Cover tightly and refrigerate. When ready to eat, bake according to recipe directions, allowing 3-5 extra minutes.
To freeze: Fill the pasta shells and flash freeze until firm. Transfer to an airtight container or freezer-safe bag and store in the freezer for up to 3 months. To bake: Place thawed shells in a baking dish on top of the creamed spinach (or sauce). Bake at 375 degrees for 20-25 minutes until warmed through. If shells are frozen, cover the baking dish with aluminum foil and bake until warmed through.