Heat the butter in the pressure cooker. Saute the onions and garlic for 1 minu te. Add the potatoes and saute for another 1 to 2 minutes. Add the remaining ingredients and stir to blend. Lock the lid in place and over high heat bring to high pressure. Adjust the heat to maintain high pressure and cook for 5 min utes. Let the pressure drop naturally or use a quick release method. Remove t he lid, tilting it away from you to and pepper to taste.