Turn the Instant Pot on the sauté setting and place the butter in to let it melt as it warms up.
In the meantime, combine and mix the garlic powder, onion powder, salt, pepper, dried basil, dried oregano, and dried rosemary to create a spice rub for the chicken.
Rub the chicken breasts in the spice rub and then place them in the instant pot to brown. Brown on both sides, but don’t cook all the way, about 1 to 2 minutes on both sides.
Press cancel to turn off sauté mode. Add in the pasta, marinara sauce, chicken broth, and Italian dressing on top of chicken.
Stir thoroughly and make sure the liquid is covering the pasta shells completely. Then close the lid, making sure that the valve is sealed.
Cook for 6 minutes on high pressure then release the pressure with slow release (Where the valve is about halfway open and slowly releasing pressure). After about 5 minutes of slow release, use quick release to release the rest of the pressure.
Remove chicken breasts and cut into cubes or shredded. Return the chicken to the Instant pot and stir.
Sprinkle the mozzarella cheese and parmesan cheese on top of chicken and pasta.
Close the lid and set the Instant Pot to warm. Cook until the cheese is melted and then plate and serve.
Garnish with fresh chopped parsley. Best when served warm.