Preheat oven to 400º.
Halve the potatoes the long way. Place them in a single layer in a large sauté pan. Add the whey and place the pan over medium-high heat. Cover and simmer until fork tender, about 15 minutes.
Using tongs, transfer the potatoes to a large bowl, discarding any whey that hasn’t been absorbed. Add the ghee and sea salt and toss to coat well. Spread the potatoes out, cut-side down, on a baking sheet, and lightly smash with the flat side of a large spoon or the bottom of a glass. Roast until golden and crisp, about 30 minutes.
Lightly season with smoked salt, garnish with rosemary, and serve warm.
Serves 4 as a side dish