Preheat oven to 350 degrees F.

In a large bowl, mix spinach, cheeses, eggs, salt and pepper. Stir together until well blended. Place about 1 1/2 cups of marinara sauce in a 9×13-inch pan. Spread it around to cover the bottom.

Place the mixed filling into a plastic bag. You can use either a frosting piping bag or a gallon zip bag. Snip the corner, gather the top and squeeze the filling into the corner. Hold an uncooked manicotti shell in your hand and squeeze the filling inside the shell. Let it overflow on both sides. Place the filled shell into the sauce-lined pan.

Repeat with remaining manicotti and fill the pan with the stuffed shells.

Cover the pasta with marinara sauce, using about 2 1/2 cups of sauce. Sprinkle 1/2 cup mozzarella on top. At this point, you can cover with foil and refrigerate until you’re ready to bake, or you can cover with foil and place it in the oven immediately.

Bake, covered with foil, 50 minutes. Remove foil and bake an additional 10 minutes.