Select Sauté or browning on your Pressure Cooker and allow it to heat fully. Add oil and butter, then add beef, season with salt and pepper, and saute the meat until browned on all sides. Add onion and garlic, saute for 30 more seconds.
Add flour and tomato paste, stir. Pour in the beer and deglaze the cooking pot. Cook for 2 minutes, scraping the brown bits from the bottom of the pan.
Add in beef broth, Worcestershire sauce, thyme, and bay leaves.
Stir in cubed potatoes, carrot, and parsnips.
Close the lid and steam valve of the Instant Pot. Cook at high pressure for 35 minutes, then natural pressure release, or do a quick release after 10 minutes of natural release.
Open the lid. Discard the bay leaves. Season to taste.
Press the saute button. Mix together the cornstarch and cold water in a small bowl and stir into the stew, letting it simmer until thickened.