Press the saute' button on your instant pot.
Add olive oil and let it heat for a minute.
Add onions and peppers to the pot.
Saute' until translucent and the onions and peppers begin to brown. Turn off saute'.
Pour a small amount of chicken broth into the pot to deglaze. (If the Instant Pot senses stuck on or burnt food, you may get a burn notice. Deglazing will keep that from happening most of the time.)
Deglaze the bottom of the pot by stirring around and removing any burnt bits that may have stuck to the bottom of the pot.
Add the remaining amount to the pot and stir.
Add the chicken breasts, Lawry's seasoning salt and cayenne pepper.
Put the cover on your Instant Pot and make sure the valve is set to the sealing position so it can build up pressure. Press the pressure cook button on your instant pot and set it to 15 minutes at high pressure. (Always follow the manufacturer's directions on how to operate your Instant Pot.)
Once the Instant Pot comes to pressure and cooks for 15 minutes, manually release the pressure valve with the long end of a wooden spoon, being careful not to come in contact with the steam. (It took approximately 15 minutes for my Instant Pot to come to pressure and to start the actual cooking process.)
Remove the lid from the Instant Pot and set aside.
Remove only the chicken from the pot and add to the bowl of a stand mixer or a large bowl using a hand mixer and shred the chicken on low speed until it is shredded to your liking. (If you do not have or do not want to use a mixer, you can shred the chicken with two forks.)
Add the shredded chicken back to the pot.
Break small amounts of dried spaghetti at a time and add to the pot in a criss cross manner. (I grabbed a handful of spaghetti at a time and broke each handful into three parts.)
Pour the mushrooms, pimientos and their remaining juices evenly over the spaghetti.
Put the cover on your Instant Pot and make sure it is set to the sealing position. Press the pressure cook button on your Instant Pot and set it to 5 minutes at high pressure.
Once the Instant Pot comes to pressure and cooks for 5 minutes, manually release the pressure valve with the long end of a wooden spoon, being careful not to come in contact with the steam. (It took approximately 15 minutes for my Instant Pot to come to pressure and to start the actual cooking process.)
Pour the mushrooms, pimientos and their remaining juices evenly over the spaghetti.
Put the cover on your Instant Pot and make sure it is set to the sealing position. Press the pressure cook button on your Instant Pot and set it to 5 minutes at high pressure.
Once the Instant Pot comes to pressure and cooks for 5 minutes, manually release the pressure valve with the long end of a wooden spoon, being careful not to come in contact with the steam.
Replace the lid of the Instant Pot but do not turn it on. Let sit for 5 minutes so the cheeses can melt.
Remove the lid from the Instant Pot and stir all of the ingredients until they are combined.
Add the remaining 1/4 cup of shredded cheddar cheese, if you set it aside, and some green parsley for garnish, if desired.
Enjoy!