I make this often; the pork tenderloin is a versatile piece of meat! It's from Jacques Pepin's Fast Food My Way

Breaded pork scaloppine with mushroom sauce

Jacque Pepin: "Pork tenderloins are lean, tender, moist, and low in calories. In this recipe, I slice the tenderloin, pound the slices into scaloppine (which could not be easier), bread them, and serve with a mushroom pan sauce. You can do this with chicken breast or veal too."
4 servings

3/4 pound pork tenderloin, trimmed of fat
1 1/4 teaspoon salt
1/2 teaspoon freshly ground black pepper
1 large egg
3 slices white bread, processed into crumbs (about 2 cups)
2 tablespoons freshly grated Parmesan cheese
3 tablespoons good olive oil
2 tablespoons unsalted butter
1/4 cup chopped onion
2 1/2 cups sliced white button mushrooms

Heat the oven to 180 degrees. Cut the tenderloin crosswise into 8 slices, each about 1 1/2 ounces. Pound the slices until they are about 1/4 inch thick, then sprinkle them with 3/4 teaspoon of the salt and the pepper.
Beat the egg thoroughly with a fork in a shallow bowl. Combine the bread crumbs and the cheese in another shallow bowl. Dip the slices of meat into the egg to lightly coat each side, let the excess drip off, and dip the meat into the mixture until well coated on each side. Arrange the breaded meat on a platter.
At cooking time, divide the olive oil between two nonstick skillets and heat until hot but not smoking. Arrange 4 scaloppine in each skillet so that they don't overlap and sauté over high heat for about 11/2 minutes on each side, or until nicely browned. Arrange on a clean platter, and keep warm in the oven.
Add the butter and onion to one of the skillets and saute over high heat for 1 minute, or until slightly softened. Add the mushrooms and the remaining 1/2 teaspoon salt and saute for 2 to 3 minutes, until the mushrooms are lightly browned and most of their liquid has evaporated.
Spoon the mushrooms over the scaloppine, sprinkle with the chives and lemon juice, and serve.