Prepare the dish up to 1 day in advance and reheat to serve.
Vegetable oil (for the dish)
5 (3 1/2 to 4 pounds) Yukon Gold or Yellow Finn potatoes, unpeeled and quartered
Salt and pepper, to taste
2 cups skim or low-fat milk
Olive oil (for sprinkling)
Rub vegetable oil in an 11-by-7-inch baking dish or another dish with a 2 1/2-quart capacity. Set the oven at 400 degrees.
In a large saucepan, combine the potatoes with a big pinch of salt, the milk, and enough water to cover them by 1 inch.
Bring the liquids to a boil, lower the heat, cover the pan, and let the potatoes bubble steadily for 20 minutes or until they are very tender but not falling apart.
Use a slotted spoon to remove several of the potatoes from the milky cooking liquid and transfer them to a shallow bowl. With a fork, break up the potatoes. Pull off and discard the skins.
Transfer the smashed potatoes to the baking dish and sprinkle with 2 tablespoons of cooking liquid, the oil, salt, and pepper. Add another 2 tablespoons of cooking liquid if the potatoes look dry. Add another layer of smashed potatoes, more cooking liquid, oil, salt, and pepper.
Bake the potatoes for 15 minutes or until crusty on top. Sheryl Julian and Julie Riven.