Preheat the oven to 450° F. Place potatoes in a large pot and cover with cold water by 1 inch. Add 1 tablespoon salt. Bring to a gentle simmer and cook for 6 minutes. The potatoes should be par-cooked at this point, soft on the outside but slightly firm on the inside. Drain the potatoes and allow them to cool slightly. While they are cooling, add the ghee, rosemary, and a pinch of salt and pepper to a saucepan and warm until melted.
Once the potatoes are cool enough to touch, use a paring knife to gently peel off the skin. Toss the potatoes in the rosemary ghee until fully coated. Don’t worry if the outside of the potatoes get a little smashed up. The starch from the potatoes will gelatinize when it mixes with the butter and coat the potatoes. This layer is what helps the potatoes get extra crispy.
Place the potatoes in a heavy rimmed baking sheet. Roast in the oven for 40 minutes, shaking the potatoes and rotating the pan halfway through. Adjust seasoning to taste.