Push the "Saute" button on your Instant Pot, and add the olive oil. Season the beef with salt and pepper. When the pot is hot, add half the beef cubes to the Instant Pot and sear for 5-7 minutes until caramelized and brown on the bottom. Remove and set aside. Repeat with oil and the rest of the beef cubes. Remove and set aside with already browned beef.
Add the chopped onion and garlic to the pot, and saute until they begin to soften and turn brown. (It'll happen in just 2-3 minutes because your pot is already so hot!)
Add the beef broth, Worcestershire sauce, thyme, and tomato paste. Stir briefly to combine, then cancel the "Saute" mode on your Instant Pot.
Add the caramelized beef back to the pot, then carrots, potatoes, and sweet potatoes (if adding them) Make sure that you cut the veggies in large pieces, otherwise they will breakdown too much and turn mushy. If you choose to add the sweet potato will breakdown regardless and is meant to add thickness and flavor to the stew base.
Put the lid on and set the valve to seal. Push the "Manual" or "High Pressure" button on your Instant Pot, and set the timer for 25 minutes.
When the timer beeps, let the pot depressurize naturally for about ten minutes. After 10 minutes, flip the valve to release the remaining pressure, then open the lid carefully. Add the frozen peas.
If you want a thicker stew, make a cornstarch slurry by whisking cornstarch and water together. Stir into the stew, and press 'saute' and let it simmer for a few minutes to thicken. Season with salt and pepper to taste. Serve warm with crusty bread or rolls. Enjoy!