Turn the Instant Pot to SAUTE.
Add 1 tbsp of oil.
Once the oil is hot add half of the beef in a single layer, and season with salt & pepper
Let the beef cook untouched for 4 to 5 minutes. Turn and continue searing, about 4 additional minutes.
Transfer the seared meat to a separate plate. Add 1 tbsp olive oil to the pot and sear the remaining beef and season with salt and pepper.
Remove the second batch of browned beef to the plate with the first batch of seared beef.
Add the remaining tablespoon olive oil and the onion to the Instant Pot.
Cook, stirring occasionally, until the onion begins to soften and browns, about 6 minutes.
Add the garlic to the Instant Pot. Cook, stirring constantly until fragrant, about 30 seconds.
Add the beef broth and use a spoon to scrape the brown bits from the bottom of the pan.
Stir in the carrots, turnips, parsnips, Worcestershire sauce, bay leaf, thyme, and the browned beef.
Pour the diced tomatoes and stir to combine.
Close and seal the Instant Pot. Cook on high pressure for 35 minutes,
When finished pressure cooking, allow the pressure to release naturally for 10 minutes.
Vent to release any remaining pressure, then open the lid.
Remove and discard the bay leaf.
In a small bowl, whisk together the cornstarch and water to create a slurry.
Add to the Instant Pot and stir until the stew thickens.
Add the peas and stir to warm through.
Serve hot, sprinkled with fresh parsley.