Preheat oven to 375 degrees. In a large pot cook pasta shells to package directions. After straining pasta, run cold water over the shells.
While pasta is cooking, wash and dry all produce. Slice scallions (separating the white and green parts).
Heat a large pan over medium high heat. Add oil and a couple handfuls of spinach. When the spinach starts to cook down, add more spinach. Cook until wilted.
In a large bowl, mix ricotta cheese, mozzarella cheese. ΒΌ cup parmesan cheese, egg, garlic powder, scallion whites and cooked spinach.
Spray casserole dish with pan spray. Fill cooked pasta shells with cheese mixture and put in casserole dish.
Spread spaghetti sauce over top of shells. Sprinkle with remaining parmesan cheese. Cover with foil and bake for 45 minutes, or until hot and bubbly. Top with scallion greens before serving.