Preheat the oven to 400 degrees F. Season the potatoes with the oil, salt and pepper. Place on a baking sheet and bake until tender, about 1 to 1 1/2 hours. Remove from the oven and cool completely. Peel the potatoes, discarding the skin, and place in a bowl. With a hand potato masher, mash the potatoes until smooth. Season with salt and pepper. Add the egg and 1/4 cup plus 2 tablespoons of the flour. Sprinkle the remaining 1/4 cup flour on a baking sheet, lined with parchment paper. Turn the dough onto the floured surface and roll into a log, about 1-inch thick. Cut the dough into 1-inch pieces. Roll each piece across the tines of a fork. In a large saucepan, combine the milk, water, 1 teaspoon olive oil, salt and pepper. Bring the liquid just to a boil. Add the gnocchi and poach for 5 minutes. Remove the gnocchi with a slotted spoon and drain. Place the cream in a saucepan over medium heat. Bring to a simmer. Whisk in the cheese and season with salt and pepper. Toss the gnocchi with the cream sauce. Spoon onto a large serving platter. Garnish with black pepper.