The first step is to take your pork loin roast and season it with the pepper and salt.
Turn your Instant Pot on Saute and then add your butter. Melt the butter and then add the pork loin.
Sear the pork loin on both sides. Add the onions and garlic. Cook this until the onions and garlic are softened. This should take about two minutes.
Add in the celery, broth, brown sugar, carrots, mustard, herbs, and Worcestershire sauce. Stir this all together in the Instant Pot.
Put the lid on the Instant Pot and seal the valve. Set to high pressure and allow for the pressure to build up.
Cook the pork loin roast for about 15 to 30 minutes. Around 20 to 25 minutes seems to be about right.
Press Cancel once the timer is up, and then allow for a natural release of pressure. The pork loin should be around 145-degrees internally.
Remove your pork loin roast and set it on a plate to allow it to rest. Keep the juices inside of the Instant Pot.
Add the corn starch and water to the Instant Pot with the juice. Turn on Saute and allow it to simmer until the juices thicken up. You can then pour this on the top of the pork loin.