When the display reads “HOT”, add ground beef, salt and seasonings and brown the meat, breaking it apart, about 10 minutes. Stir occasionally.
To make the cheese filling: while meat is browning, in a medium bowl, combine ricotta cheese, egg, parmesan cheese and 3 cups of mozzarella cheese. Mix well and transfer the mixture in a piping bag with a round tip (or a ziplock bag with one corner cut).
Fill the pasta shells with the cheese mixture.
Once the meat is browned, drain, if needed, and spread it evenly in the bottom of the pan. (Note: deglaze the pan with 1/4 cup of water if there is any bits and pieces are stuck to the pan.)
To assemble: layer the filled pasta shells over the meat.
Pour water and then pasta sauce over the pasta. Do NOT stir.
Close the lid and make sure the valve is set to “sealing”.
Set the Instant Pot to Pressure Cook/Manual for 8 minutes on high. (NOTE: It took 20-24 minutes for my IP to come to pressure.)
Do quick release by carefully turning the valve to venting. And carefully open the lid.
Sprinkle remaining 1 cup of mozzarella cheese and close the lid. Let it sit for about 3 minutes and then open the lid. Stir gently and serve.