Add the oil to the IP, set to saute, and heat for a few minutes.
Add the diced onions and bell peppers and cook stirring frequently until the onions have turned translucent, about 3 to 5 minutes.
Turn off the IP, remove the onions and peppers, and set aside.
Break the spaghetti into half and place staggered in the pot. Try not to have any spaghetti bunched together.
Cover the spaghetti with the chicken broth and enough water to completely cover the spaghetti.
Seal the lid, set the release valve to close and set the IP on high pressure for 4 minutes.
When the timer goes off, quick release the steam.
Once the pin drops, remove the lid.
Save 2 cups of the cooking liquid in a bowl, then drain the spaghetti.
Set the Instant Pot to sauté once again, add the saved cooking liquid and all the other ingredients except the spaghetti to the pot and cook, stirring constantly, until the cheese has melted.
Turn off the IP and add the spaghetti, stir until everything is combined and hot.
Serve while hot.
Notes
The amount of time it takes for your pressure cooker to pressurize will vary by brand. Allow extra time.
Smaller cheese cubes will melt quicker.
Before releasing the pressure clear the area around the Instant Pot, the steam may sputter and eject liquid.
Use a long-handled wooden spoon for moving the release valve to prevent getting burned.
I tend to use half of a cooked chicken from my chicken noodle soup for this recipe.
Any cooked chicken works well in this recipe, even a rotisserie chicken.