Cook at high pressure for 18 minutes in an electric pressure cooker… Add lamb, tomatoes, tomato paste, basil, oregano, bay leaves, salt and pepper to taste. Using your Instant Pot/pressure cooker, this delicious lamb stew is ready in about an hour. I … Pressure Cook for 18 minutes with a Natural Pressure Release: Lock the lid on the pressure cooker, bring the cooker up to high pressure over high heat, and then reduce the heat to maintain high pressure. In pressure cooker, heat oil. While cooking under pressure cuts the time substantially, you can make it on the stove as well. Sauté onions and garlic until onions are soft, about 2 minutes. Stir in vinegar and, while cooking for 1 to 2 minutes over medium heat, scrape any browned bits from the bottom.