Thaw frozen potatoes in microwave on defrost setting. Spray large frying pan with cooking spray and heat on medium until oil is glistening. Add in onion and garlic to pan and cook until onions are translucent. Add in potatoes and salt, pepper and parsley, except and mix until well blended. Flatten out potatoes in the pan and add 1/2 the butter around the outside perimeter of the potatoes so they melt down the side of the pan into the potatoes and cover. Let cook about 10 minutes or until potatoes are browned on the bottom. Use a large dinner plate over your pan to flip the potatoes onto the plate, then slide the potatoes from the plate back into the pan uncooked side down (nice trick I learned from watching Gordon Ramsey videos). Add the remaining butter to the outside like you did previously. Cook additional 10 minutes or so uncovered until the cooking side is also brown. Serve and enjoy.