Twelve ricotta-spinach manicotti tubes baked under marinara and mozzarella, serving six.

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Heat oven to 375°F. Cook twelve dry manicotti tubes in boiling water until just pliable per package instructions, then drain and cool enough to handle. Squeeze all excess liquid from 10 oz thawed chopped spinach.
Mix 15 oz ricotta, the dry spinach, one egg, 1/2 cup Parmesan, two minced garlic cloves, 1/2 tsp salt and 1/4 tsp pepper. Spread about 1 cup of the measured 3 cups marinara across a 9-by-13-inch dish.
Fill each manicotti tube gently using a piping bag or small spoon. Arrange in one layer over sauce, cover with the remaining 2 cups marinara and 1 cup shredded mozzarella. Cover loosely with foil and bake approximately 25 minutes, then uncover for about 10 minutes until hot, bubbling and lightly golden.
Check representative centers of the egg-containing filling with a thermometer for 160°F, rest ten minutes and serve two tubes per portion. Record shell breakage, spinach drainage, center temperature and actual yield in a kitchen trial.

Recipe-development draft; not kitchen-tested. Timing and yield are estimates. Nutrition has not been calculated.

Additional chilling, resting or cooling time: 10 minutes, included in the total.

Untested estimate: pasta boil about 10 minutes and covered/uncovered bake about 35 minutes plus 10-minute rest; shell brand changes time.