Turn the Instant Pot onto Saute mode and add the olive oil.
Once the pot is hot, add the chicken pieces and brown them on all sides for a few minutes. Don't worry about cooking the chicken through at this stage - just get a little bit of colour on the chicken.
Add the garlic, onion, celery, carrots, thyme and salt and pepper. Stir well.
Add the stock and stir everything to combine.
Add the lid, set the valve to sealing and set the Instant Pot to cook on High Pressure for 8 minutes.
After the 8 minutes, release the pressure manually (use a long-handled kitchen tool to release the pressure under a kitchen exhaust fan, if you have one).
Once the pressure is released, add the pasta and stir well. Replace the lid on the instant pot, set the valve to sealing and set the Instant Pot to 'Keep Warm' for 10 minutes.
Once the 10 minutes is up, release any pressure manually.
Serve with some fresh chopped parsley or rosemary.