Heat the oil in a small stainless steel pan (approx. 170°C), briefly fry the sage leaves until they are crispy. Remove with a slotted spoon and drain on paper towels.
Cook the cauliflower in salted water for approx. 35 mins. until soft. Set aside approx. 50 ml of the cooking water, drain the cauliflower, place in a bowl. Add the cheese and reserved cooking water, mash with a potato masher until the desired consistency is achieved, season. Plate up the cauliflower mash, crumble the sage over the top, drizzle with oil.