Turn the Instant Pot to the Sauté setting and add 1 tablespoons of olive oil. Season the cubes of beef with salt and pepper, to taste.
Once the oil is heated, add the beef chunks in a single layer, making sure not to crowd the pot. You want to be able to flip them to brown the other side. Place the lid over the top and allow to sear for 2-3 minutes. Remove the lid and flip, leaving the lid off.
Remove to a large bowl or plate, add 1 tablespoon more of olive oil to the pot and sear the next batch following the same steps as the first batch.
Remove the second batch and add it to the same bowl. Toss with the 1/4 cup of flour.
Add 1 tablespoon of olive oil to the pot one more time and add the chopped onions, sautéing 2-3 minutes, or until the onions are translucent. Add the minced garlic and cook for 30 seconds. Stir.
Pour in the beef stock and stir to combine. Using a wooden spoon, make sure to scrap along the bottom of the pot to remove any brown bits that stuck while browning the beef.
Add in the tomato paste, Worcestershire sauce, carrots, celery, potatoes, mushrooms, and beef. Stir to thoroughly combine. Add in all seasonings (minus bay leaves) and give it one more gentle stir. Place bay leaves on top.
Close the lid and seal the Instant Pot. Cook on HIGH PRESSURE for 25 minutes with a natural release for 10 minutes. Vent to release any remaining pressure that may still be in the pot and carefully remove the lid.
Remove the bay leaves and discard.
OPTIONAL BROTH THICKENER: In a small bowl, whisk together 2 tablespoons of cornstarch with 2 tablespoons of water. Add to the Instant Pot, stirring gently, until it begins to thicken. Add thickener, as needed, to reach desired broth thickness.
Add in the peas and stir to warm through. Serve garnished with fresh parsley as is or over a bed of egg noodles or mashed potatoes. Enjoy!