Prep the Vegetables: Finely dice the onion and mushroom, set aside.
Cook: In a pan with oil over medium-low heat, crush garlic then sauté until slightly golden then add the onion and cook until translucent. Add the mushrooms and cook on low until they reduce their liquid and begin to caramelize.
Season with salt and pepper to taste (about 3 g of salt recommended). Stir in 10 g of the Parmesan. Add the heavy cream and let it thicken slightly. Set aside.
Prep the Potatoes: Peel the potatoes, Place them in ice water, let chill for 30 minutes
Cook the Potatoes: now cut the potatoes in thin strips, put them into a pot of boiling water, cook the potatoes for 5 minutes. Immediately transfer them back into ice water to stop the cooking. Once cooled, place them in the freezer to chill.
Fry the Potatoes: Deep-fry in oil (at least 2 cup) at 350°F (175°C) until they float and are golden (about 10-15 minutes). Then remove and place on plate with paper towel to drain
Assemble the Dish: Top the hot chips with the mushroom, freshly grated Parmesan, a drizzle of black truffle oil, and a sprinkle of finely chopped parsley.
Optional: arrange in a baking dish and heat in oven at 340°F (170°C) until the cheese melts
Notes
NOTE* Returning them to the ice bath immediately stops the cooking process, this ensures that the insides stay light and fluffy when frying them