Wash, dry, then cut the potatoes in half, crosswise. Arrange in a single layer, cut side down, on a clean, rimmed 14-inch jelly roll pan or a roasting pan, spaced evenly apart. Scatter garlic cloves around potatoes,then add 2 cups water to pan.
Cover pan with aluminum foil, sealing sides very tightly so potatoes steam. Bake potatoes on lowest rack for 25–30 minutes.
Remove from oven and carefully feel around for a potato without removing the foil. A fork should slide easily through potato. Pierce another to be sure that all are tender. If still a little hard, bake another 5 minutes or until tender.
Turn oven temperature up to 500°F. Carefully lift up foil at 1 corner of pan and tip open corner into the sink to pour off water, keeping steam away from face and hands.
Remove foil and and turn potatoes over. Drizzle oil over potatoes and garlic. Season with salt and pepper.
Roast potatoes and garlic for 10 minutes, uncovered. Ensure that all potatoes are still cut side down and roast another 15 minutes until cut sides are brown and crisp.
Let potatoes cool slightly, then use a spatula to remove them from baking sheet. Sprinkle with chopped parsley before serving. Season to taste.
I prefer Yukon Gold potatoes, but red potatoes also work amazingly well. If potatoes are large, quarter them instead of just cutting in half.