Set Instant pot to saute setting. When hot, add olive oil and then chopped onion and garlic. Cook, stirring frequently for 1 minute. Add chicken pieces and cook, stirring frequently for 2 minutes.
Press cancel and then add marinara sauce, water, Italian seasoning, salt and ground pepper. Stir well, place pasta on top of the liquid (DO NOT STIR), pressing lightly for them to be slightly immersed in the liquid, but do not stir. Close and lock lid (making sure that valve is set to sealing). Select manual setting (or pressure cooker) for 7 minutes.
After 7 minutes, let Instant pot in the warm mode for 4 minutes. Turn valve to venting to release pressure. Open lid, sprinkle both cheeses, close lid and let cheese melt for one minute.
Open Instant pot, stir to mix in melted cheese and serve Instant pot chicken parmesan pasta hot with chopped parsley or basil. Or cool and pack into meal prep containers.(Few readers have brought to our attention that they get the 'BURN' signal while making this recipe. So, we have made necessary changes to the recipe to avoid burning. The recipe has been tested in both 8-quart and 3-quart sizes)