Season and sear the beef in the Instant Pot on Sauté in two batches until browned. Transfer to a plate.
Cook the onion until softened, then add the garlic and tomato paste and cook until darkened slightly.
Add the beef broth and Worcestershire sauce, scraping up the browned bits.
Return the beef to the pot with the thyme. Lock the lid and cook on HIGH pressure for 20 minutes.
Quick release, add the carrots and potatoes, and cook on HIGH pressure for 8 minutes. Let the pressure release naturally for 10 minutes.
Quick release any remaining pressure, switch to Sauté, and stir in the cornstarch slurry and frozen peas. Simmer until thickened.
Season to taste and serve garnished with parsley.