Fill a large pot with 2 inches of water and bring to a boil. Place a metal mixing bowl over the boiling water to create a double boiler. Combine the milk, heavy cream, and butter in the metal bowl and whisk until the butter has melted. Then slowly add the Bitto, whisking so that the cheese has melted before adding more. When all of the cheese is incorporated, add the egg yolks one at a time and whisk until combined. Continue to whisk until the fonduta begins to thicken and can coat the back of a spoon. Carefully pour the fonduta into a heat-resistant container and set aside.
Place one sheet of tenderized beef on a round plate. Using a spoon, drizzle the fonduta on the meat. Sprinkle with Maldon salt, black pepper, and arugula then thinly shave the black truffle on top.