Select Sauté on your Instant Pot. Once Instant Pot says “HOT”, add your butter and melt it.
Add onions, mushrooms, and garlic and stir. Cook until onions have softened, about 5 minutes.
Add red bell pepper, seasoned salt, paprika, basil, red pepper flakes and stir. Press “Cancel” on Instant Pot.
Lay chicken breast pieces in layer in the Instant Pot. Sprinkle with a pinch of salt and pepper. Pour in chicken broth. Spread spaghetti noodles in Instant Pot. Push down so it gets covered by liquid. Place lid on Instant Pot, ensuring that the valve is set to “Sealing.”
Press "Pressure Cook" or "Manual" and select High Pressure for 6 minutes.
Once timer is done, do a quick release by moving valve to “Venting”. Open lid and stir to loosen up noodles. Add heavy cream and cheese and continue to stir.
Press “Cancel” and then select Sauté. Cook for about 3-5 minutes, stirring to thicken the sauce.