In a large bowl combine 2 cups of ricotta cheese, 2 cups mozzarella cheese, 1/2 cup Parmesan cheese, 1 tsp salt, 1/4 tsp black pepper, and 1 egg.
Once the cheese mixture is fully combined transfer it to a gallon-sized Ziploc bag. Press to mixture into one corner and snip off a small part of the end.
Now cook 8 oz manicotti (about 14 manicotti) in a large pot of salted boiling water. Be careful not to overcook them.
Once they’re cooked rinse them with cold water and begin filling the cheese mixture into each manicotti shell.
Then pour another 2 cups of marinara sauce on top of the manicotti along with 1 cup of shredded mozzarella cheese.
Bake at 350°F for about 20-25 minutes. If you want the cheese to brown a little on top, broil for a few minutes at the end. Once it’s done, garnish with some freshly chopped parsley.
Notes
Don't overcook the manicotti- You want the manicotti shells to be firm enough to be easily handled when you fill them, so only cook them to al dente. They'll cook more in the oven.
Rinse the manicotti shells in cold water- So they don't get too soft, rinse them in cold water to stop the cooking process.
Pipe the filling in- While you can also spoon it in, piping does a better job of thoroughly filling the manicotti without stretching or tearing the shells.
Line the bottom of the pan with sauce- To keep the manicotti from getting hard while they bake, line the pan with sauce to keep them moist. This also keeps them from burning on the bottom.