Sautéing arugula in olive oil mollifies its sharp flavor and transforms it into something quite different.
1. Rinse the arugula and pat dry on absorbent paper. Stack the leaves and cut them across into thin shreds. Heat the oil in a small skillet. Add the arugula and stir over high heat for 30 seconds or until wilted and intensely green. Transfer to a plate and set aside.
2. Melt the butter in a large skillet. Add the mushrooms and toss to coat. Stir over medium heat until tender, but do not allow them to brown. Sprinkle with salt and pepper. Remove from the heat and stir in the arugula.
3. In a small bowl, whisk together the cream and egg yolks. Add the mixture to the mushrooms and return to medium heat. Sprinkle on the Parmesan cheese and stir constantly until the cheese is melted and the sauce is slightly thickened. Add the drained fettuccine and toss over medium heat to coat and to warm the noodles. Serve immediately.