On the Instant Pot, select the “Sauté” mode. Add the butter. Once the butter has melted, add the chicken. Sear on each side for 2-3 minutes or until browned.
Deglaze the pan with the chicken broth, scraping any brown bits off the bottom of the pot.
Select “Pressure Cook” and “High Pressure” and set the timer for 15 minutes.
Once the timer goes off, quick release the pressure (switch the valve to venting). Using two forks shred the chicken in the pot. Do not drain any of the broth.
Stir in the garlic, italian seasoning, salt, pepper, chili flakes, chili flakes, and cumin.
Place the spaghetti on top of the chicken in a few different layers, each going in opposite directions. Do not stir. Swirl the pot around gently so the liquid lightly coats the noodle.
In this order, sprinkle on the mushrooms, onion, pepper, and tomatoes.
Select “Pressure Cook” and “High Pressure” and set the timer for 4 minutes.
Once the timer goes off, quick release the pressure (switch the valve to venting). Stir in the half and half.
Add in the cream cheese, cheddar, and parmesan. Fold continuously until the cheese is melted. This will take a couple of minutes.