Preheat oven to 350°

If adding ground beef, brown and drain fat.

In a large bowl; mix spinach, cheeses, eggs, salt and pepper (and ground beef if added).

Place about 1 1/2 cups of marinara sauce in 9x13 inch pan. Spread it around to cover the bottom.

Put 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 stuffed shells, until you run out of shells and filling. (You should be able to fill 12-14 shells-if you run out of room in your pan, use a separate smaller pan to accommodate the extra.)

Cover the pasta with marinara sauce. Sprinkle 1/2 cup Romano/Parmesan cheese on top. Cover with foil and place it in the oven for 50 minutes.

Remove foil and bake for an additional 10 minutes.