Place potatoes into a large pot and cover with salted water. Season water with garlic powder and bring to a boil. Reduce heat to medium-low and simmer until tender, 15 to 20 minutes. Drain and transfer potatoes to a large skillet over medium-high heat. Mash potatoes in the hot skillet and add butter and garlic powder. Form mashed potatoes into a large patty and coat the edges with olive oil, allowing oil to pour under the patty. Cook until bottom is golden brown, 5 to 10 minutes. Break patty using a wooden spoon and fold crisp bottom through the potatoes. Repeat cooking the bottom and folding into the mashed potatoes.