Preheat oven to 375° Prepare pasta according to package directions, adding 2-3 teaspoons of salt to the cooking water; drain and rinse with cold water.
If using Tinkyada brown rice shells, cook for the maximum time recommended on the package. [If using regular wheat pasta shells, undercook by a couple of minutes.]
To keep pasta from drying out, allow to sit briefly in cool water until ready to use.
While pasta is cooking, add olive oil, garlic, green onions, and spinach to a large skillet and cook over medium heat until onion and garlic are softened and spinach is wilted.
If spinach seems watery, transfer to a plate lined with paper towels to drain and cool. Once cooled slightly, coarsely chop spinach.
In medium bowl, blend Ricotta, eggs, nutmeg, salt, and pepper until well mixed. Stir in parmesan and mozzarella cheeses until combined. Fold in parsley and chopped spinach with onions and garlic.
Put cheese mixture in a resealable plastic bag (quart size may be easier to handle). Cut one bottom corner of the bag to create a quarter sized whole. Place corner of bag into the opening of the pasta shells and squeeze bag to fill pasta. (At this point the recipe can be frozen.)
Arrange filled shells in a 13 × 9-inch baking dish.
Spoon sauce over the shells and cover tightly with foil. Bake covered for 30 minutes, uncover and sprinkle with 1 cup of mozzarella cheese, and bake for 10-15 minutes until cheese is melted and beginning to brown.