Place beef stew in a large gallon bag sprinkle the cornstarch and Montreal steak seasoning. Toss until coated.
Pour the grape seed oil in the Instant Pot then pour in the beef. Let brown for 2-3 minutes.
While beef is browning begin peeling and chopping vegetables.
Turn beef then mix in the dehydrated garlic and tomato paste. Remove the beef from the Instant Pot.
Then add in 1/2 cup of water and deglaze the pot--scraping the brown bits off the bottom. Then add in the carrots, celery, onion, and parsnips.
Sauté for 5 minutes. Add in the tomatoes, potatoes, pearl onions, and mushrooms. Mix well then place the lid on top of the Instant Pot.
Set the Instant Pot to "manual" for 35 minutes on manual mode.
Once the Instant Pot is done cooking, let it naturally release pressure for 10-15 minutes. Carefully, force the remaining pressure out of the IP then remove the lid. Mix well, and mix in the green peas, corn, and fresh parsley.
Place lid on top and let sit for 5 minutes. Divide evenly among bowls and enjoy.