Put the potatoes in a medium-size saucepan and add enough water to cover. Season with salt. Bring to a boil over high heat, then reduce the heat to medium and cook until fork tender, 10 to 12 minutes. Drain and cool under cold water. Arrange in a shallow dish and allow to come to room temperature. Preheat the oven to 375 degrees F. Lightly oil two baking sheets with olive oil. Divide the pizza dough into 4 equal portions. With your fingers, dusted with flour, pat the dough into free-form circles, each 8 to 10 inches in diameter, and put them on the prepared baking sheets. Prick each randomly with a fork. Brush each dough circle with 1/2 teaspoon of the truffle oil and top each with equal amounts of the potatoes. Season with salt and freshly ground black pepper. Continue layering with the onions, shredded duck confit and cheese. Drizzle the remaining teaspoon of truffle oil evenly over the pizzas. Bake on the middle rack of the oven and bake until the crust is golden brown, about 25 minutes. Remove from the oven and cool for a few minutes before slicing into 8 slices. Garnish with parsley and serve.