Prepare the Beef: chop beef into bite-sized chunks and season with 1 teaspoon salt and 1 teaspoon black pepper.
Brown the Beef: Set your Instant Pot to the sauté function on high. Once hot, add 1 ½ tablespoons of olive oil. Add half of the beef to the pot and cook, stirring occasionally, until browned on all sides. Repeat with the remaining beef, adding more olive oil if necessary. Remove the beef and set aside.
Sauté the Onion: Add the remaining 1 ½ tablespoons of olive oil to the pot. Add the chopped onion and sauté for 3-4 minutes, until softened and lightly golden.
Add Garlic: Stir in the minced garlic and cook for about 30 seconds, until fragrant.
Add Tomato Paste and Sauces: Stir in 2 tablespoons of tomato paste, 1 tablespoon of fish sauce, and 1 tablespoon of Worcestershire sauce. Mix well.
Deglaze with Guinness: Pour in the 16 ounces of Guinness beer and stir to deglaze the pot, scraping up any brown bits from the bottom.
Add Beef and Veggies: Return the browned beef to the pot. Add 1 pound of carrots, 1 pound of halved baby potatoes, 1 bay leaf, and 3 sprigs of thyme. Pour in 4 cups of beef broth and stir to combine.
Pressure Cook: Close the Instant Pot lid and ensure the valve is set to “Sealing.” Cook on high pressure for 35 minutes.
Release Pressure: Once the cooking time is up, allow the pressure to naturally release for 10 minutes, then carefully release any remaining pressure.
Thicken the Stew: In a small bowl, mix 2 tablespoons of cornstarch with 2 tablespoons of cold water. Stir this mixture into the stew, set the Instant Pot to the sauté function, then continue to stir until the stew thickens to your desired consistency.
Adjust seasoning to taste adding more salt and pepper if needed. Serve.