Preparation Peel potatoes and cut into 1/2-inch cubes (there should be about 3 cups). In a large saucepan of boiling salted water parboil potatoes 5 minutes. Drain potatoes and cool. In a skillet heat oil and 1 tablespoon butter over moderately high heat until hot but not smoking and sauté onions, stirring occasionally, until soft and caramelized. Cool onions and in a bowl combine with potatoes, stirring vigorously to partially break up potatoes. Hash browns may be prepared up to this point 1 day ahead and chilled, covered. Preheat oven to 350°F. In a 10-inch non-stick skillet heat remaining 2 tablespoons butter over moderate heat until foam subsides and cook potato mixture, packing it evenly in skillet with back of spatula to form a cake, until underside is golden, about 10 minutes. Invert a plate or baking sheet without sides over skillet and carefully invert potato cake onto it. Carefully slide potato cake back into skillet and brown other side. On baking sheet bake potato cake 10 minutes. Sprinkle hash browns with pepper and salt to taste and cut into wedges.
Preparation Peel potatoes and cut into 1/2-inch cubes (there should be about 3 cups). In a large saucepan of boiling salted water parboil potatoes 5 minutes. Drain potatoes and cool. In a skillet heat oil and 1 tablespoon butter over moderately high heat until hot but not smoking and sauté onions, stirring occasionally, until soft and caramelized. Cool onions and in a bowl combine with potatoes, stirring vigorously to partially break up potatoes. Hash browns may be prepared up to this point 1 day ahead and chilled, covered. Preheat oven to 350°F. In a 10-inch non-stick skillet heat remaining 2 tablespoons butter over moderate heat until foam subsides and cook potato mixture, packing it evenly in skillet with back of spatula to form a cake, until underside is golden, about 10 minutes. Invert a plate or baking sheet without sides over skillet and carefully invert potato cake onto it. Carefully slide potato cake back into skillet and brown other side. On baking sheet bake potato cake 10 minutes. Sprinkle hash browns with pepper and salt to taste and cut into wedges.