Cube the beef and place in a sealable container or bag. Prepare garlic, celery, onion, carrot, and parsnips and add to the container. Add Worcestershire sauce, salt, pepper, and Italian seasoning. Seal and refrigerate until ready to cook.
Place contents of bag into Instant Pot with beef broth. Stir well.
Cover and seal the lid and pressure valve. Cook on Manual High for 20 minutes, allowing a natural pressure release. When pressure valve drops, remove the lid.
Hit saute and stir in cornstarch or xanthan gum. Allow the stew to come to a boil and thicken, 4-5 minutes, then taste and adjust seasoning with salt and pepper if necessary. Serve hot garnished with fresh parsley.
Notes
Storage: Store leftovers in a sealed container in the refrigerator for up to 3 days. To freeze, store leftover beef stew in a freezer safe container in the freezer for up to 3 months. Law overnight in the refrigerator before reheating.