The French have known this forever, whereas here, in the beautiful States, it just became the next big thing: There is nothing more wonderful you can do to potatoes than to cook them in duck fat. Where do I get duck fat, you ask? Cook a single Moulard duck breast half, and you'll easily render off a cup and a half. Strain out the brown bits, and you can store the fat almost indefinitely in the refrigerator. And don't feel guilty — you're using only a tiny bit.
Preheat the oven to 450 degrees.
In a mixing bowl, toss the potatoes, duck fat, salt, and pepper to coat. Spread in an even layer on a baking sheet and roast until the cut sides of the potatoes are golden and crispy, 25-30 minutes. Transfer to a serving bowl, and mix in the parsley, lemon zest, and juice. Serve hot.