In a 12-inch oven-going skillet, heat the olive oil over medium heat until hot but not smoking. Carefully add potatoes, onion, salt and black pepper. Cook, stirring occasionally, about 20 minutes or until potatoes are just tender. Remove from heat.
Top potatoes with asparagus, arugula, tomatoes and mozzarella. Pour eggs over mixture.
Bake, uncovered, in a 350 degree F oven for 25 to 30 minutes or until center is just set.
Place on cooling rack; immediately sprinkle with Parmesan. Let stand 15 minutes.
To serve, cut into 8 wedges. Serve immediately with a light drizzle of white truffle oil over each serving, if you like. Makes 8 servings.