Peel potatoes and cut into 1/2 inch slices. Place sliced potatoes in a pot and cover with water. Bring to a boil. Allow to boil 2 minutes, then drain and set aside.
Heat a large ovenproof skillet over medium-high heat. Pour in olive oil, then add onions. Saute until lightly caramelized, 8 to 10 minutes. Stir in garlic and saute until onions are deep brown and garlic is soft. Transfer mixture to a bowl.
Place skillet back on stove over low heat. Melt butter, then cover bottom of pan with 1/3 of potatoes. Season with salt and pepper. Cover potatoes with 1/2 of onion mixture. Cover with 1/2 of remaining potatoes and season with salt and pepper. Spread with the rest of onion mixture. Cover with remaining potatoes, and season with more salt and pepper.
Bake in preheated oven for 10 to 12 minutes, or until potatoes are tender and browned on top. Remove from oven and use a spatula to carefully transfer potatoes to a serving platter. Sprinkle with chopped parsley just before serving.