Ingredients

• 2/3 cup plain yogurt (6 ounces; preferably whole-milk)
• 3 tablespoons mayonnaise
• 2 tablespoons drained bottled capers, finely chopped
• 1 tablespoon finely chopped fresh flat-leaf parsley
• 1/8 teaspoon black pepper
• 1 1/2 to 1 3/4 lb pork tenderloin
• 3/4 cup all-purpose flour
• 1 teaspoon salt
• 1/4 teaspoon black pepper
• 2 large eggs
• 1 cup fine dry bread crumbs
• About 1 cup vegetable oil for panfrying
• Special equipment: an instant-read thermometer
• Accompaniment: lemon wedges; watercress or other baby greens

Instructions

1. Stir together all sauce ingredients in a bowl until combined, then chill, covered, until ready to use.
2. Cook pork: Put oven rack in middle position and preheat oven to 350°F. Cut pork crosswise into 1 1/4-inch-thick slices (medallions). Whisk together flour, salt, and pepper in a shallow bowl. Whisk together eggs with a pinch of salt in another shallow bowl and put bread crumbs in a third shallow bowl. Working with 1 medallion at a time, dredge medallions in flour, shaking off excess, and dip in egg, letting excess drip off, then coat with crumbs, pressing to help them adhere. Arrange pork in 1 layer on a baking sheet. Heat 1/4 inch oil in a 12-inch heavy skillet over moderate heat until hot but not smoking, then panfry medallions, turning over once, until golden brown, 6 to 8 minutes total. Transfer to a clean baking sheet and roast in oven until thermometer inserted horizontally into center of meat registers 145 to 150°F, 6 to 7 minutes.
3. Put oven rack in middle position and preheat oven to 350°F.
4. Cut pork crosswise into 1 1/4-inch-thick slices (medallions).
5. Whisk together flour, salt, and pepper in a shallow bowl.
6. Whisk together eggs with a pinch of salt in another shallow bowl and put bread crumbs in a third shallow bowl.
7. Working with 1 medallion at a time, dredge medallions in flour, shaking off excess, and dip in egg, letting excess drip off, then coat with crumbs, pressing to help them adhere. Arrange pork in 1 layer on a baking sheet.
8. Heat 1/4 inch oil in a 12-inch heavy skillet over moderate heat until hot but not smoking, then panfry medallions, turning over once, until golden brown, 6 to 8 minutes total. Transfer to a clean baking sheet and roast in oven until thermometer inserted horizontally into center of meat registers 145 to 150°F, 6 to 7 minutes.
9. Serve pork with sauce, lemon wedges, and watercress.