Preheat the oven to 180°C.
Place three truffle slices under the breast skin and season with salt and pepper.
Cut the remaining truffles into thin strips and set aside.
Heat 30ml of oil in an ovenproof pan and sear the bird skin-side down until golden.
Flip the breast and roast in the oven for eight minutes before resting in a warm place.
Boil the leeks in salted water for one minute, then refresh in ice water and drain.
Boil potatoes for six minutes, add pancetta for two more minutes, then refresh in ice water.
Sauté potatoes and pancetta in the remaining oil until golden brown.
Stir in leeks, herbs, some truffle strips, and 45ml of water to create a sauce.
Emulsify the sauce by melting in the butter and remaining truffles.
Service the halved breasts over the potato mixture with truffle butter sauce poured over.