Preheat the oven to 190°C and remove the duck from the fridge at least 30 minutes before cooking and pat the skin dry.
Trim some of the excess fat and add to a pan for the chips. Place on a medium heat and allow the fat to render.
Season the duck with salt. Place skin-side down into an oven-safe pan off the heat, and no oil is required. Now gradually bring the heat up to medium. The aim is to render out the fat and form a crispy golden skin; this should take 4 - 8 mins. Turn duck and drain fat into the other pan, then place duck in the oven to cook for a further 8 - 10 minutes. Remove and rest for 10 minutes.
Meanwhile add the potatoes to the duck fat on a medium-high heat with a pinch of salt and cook until golden and cook through.
While the duck is resting, make the sauce. Fry the shallots and peppercorns for 1 - 2 minutes over a high heat and add the whiskey. Flambée and then allow the flames to subside. Add the stock and bring to the boil. Reduce by ⅓ and then add the cream, stir through and cook for a further minute to thicken.
Slice the duck and serve with duck fat chips and sauce.