Set your Instant Pot to 'Sauté' mode. Add the olive oil and let it heat up. Season the beef cubes with salt and pepper, then add them to the pot in batches. Sear the beef until browned on all sides. Remove the beef and set aside.
In the same pot, add the chopped onion and garlic, sautéing until fragrant and tender, about 3-4 minutes.
Stir in the tomato paste, Worcestershire sauce, thyme, and rosemary. Cook for an additional minute. Return the seared beef to the pot and add in the sliced carrots and diced potatoes.
Pour in the beef broth, making sure to scrape any browned bits off the bottom of the pot. This adds flavor and prevents burning during cooking.
Close the lid of the Instant Pot, set the valve to 'Sealing,' and select 'Pressure Cook' for 35 minutes at high pressure.
After the cooking time is up, allow the Instant Pot to release pressure naturally for 10 minutes, then carefully use the quick release for any remaining pressure.
If you prefer a thicker stew, mix the cornstarch with a few tablespoons of broth to create a slurry. Stir it into the stew and select 'Sauté' mode. Cook for an additional 5 minutes, stirring until thickened.
Taste and adjust seasoning with more salt and pepper if necessary. Serve hot, garnished with fresh parsley.
Notes
Optional thickening with cornstarch can be adjusted based on preference.