1. Cook manicotti according to package directions, omitting salt and fat. Drain and set aside to cool.
2. Preheat oven to 375°.
3. Heat oil in a large skillet over medium heat. Add onion, and sauté 5 minutes. Stir in spinach; sauté 3 minutes.
4. Place spinach mixture, tofu, and next 7 ingredients in a food processor; process until smooth.
5. Spoon about 1/4 cup ricotta mixture into each manicotti. Pour one-third of pasta sauce into a 13 x 9-inch baking dish coated with cooking spray. Arrange stuffed manicotti in a single layer over sauce, and top with remaining sauce. Sprinkle with mozzarella cheese.
6. Cover with foil; bake at 375° for 30 minutes. Remove foil, and bake an additional 20 minutes or until browned.
Note: You'll have about 1 cup of filling left over. Feel free to fill extra shells, but make sure to buy an extra package of manicotti at the store--a standard package contains 14 shells.