In a pressure cooker, brown roast in oil on all sides. Add the potatoes, carrots, onion and water. Close cover securely; place pressure regulator on vent pipe. Bring cooker to full pressure over high heat. Reduce heat to medium-high; cook for 40 minutes. (Pressure regulator should maintain a slow steady rocking motion; adjust heat if needed.)
Remove from the heat; allow pressure to drop on its own. Remove meat and vegetables; keep warm. Bring cooking juices in pressure cooker to a boil. Add bouillon, salt and pepper.
Combine cornstarch and cold water until smooth; stir into juices. Bring to a boil; cook and stir for 2 minutes or until thickened. Serve with roast and vegetables.
Editor’s Note: This recipe was tested at 13 pounds of pressure (psi).