Stir 1-2 cups chopped fresh spinach into tofu ricotta, and stuff al dente prepared pasta shells with tofu ricotta mixture. In a large rectangular glass baking dish, add a small layer of marinara sauce, then the stuffed shells, and then top the shells with a layer of marinara sauce and optionally vegan Italian sausage crumbles (or crumbled Italian Field Roast or crumbled Tofurkey Italian sausage). Bake covered with foil @ 350F for 25 to 35 minutes, uncovering for the last 10 minutes.