Preheat the oven to 350 degrees.
Place bread slices on a large rimmed baking sheet. Brush both sides of each slice lightly using 2 tablespoons of the olive oil. Sprinkle with the salt and 1/4 teaspoon of the pepper. Bake until golden brown, about 15 minutes, turning once. Remove from oven and set aside.
In a large skillet, heat remaining 2 tablespoons olive oil and the garlic over medium heat. When garlic begins to sizzle, stir in parsley. Cook, stirring frequently, about one minute.
Increase heat to medium high; add mushrooms and remaining 1/4 teaspoon pepper. Cook, stirring frequently, until mushrooms release their liquid, about 5 minutes. Add wine, stirring, until wine is evaporated. Remove from heat; stir in truffle oil.
Top crostini with sautéed mushrooms, prosciutto, egg, arugula and a few shavings of Parmigianino cheese.