Balsamic Pork and Dumplings

1 16.9-oz package frozen potato-and onion filled pierogi (potato dumplings)
12 oz green and/or wax beans, trimmed (3 cups)
1 lb pork tenderloin
2 Tbsp olive oil
1/2 cup balsamic vinegar
2 tsp chopped fresh rosemary (optional)

1. Cook pierogi and beans in boiling water according to pierogi package directions. Drain pierogi and beans; divide among serving plates.
2. Meanwhile, slice pork in 1/2 inch medallions. Gently flatten pork slices by hand to 1/4 inch thickness; lightly sprinkle with salt and black pepper. Heat oil in large skillet over medium heat. Add pork. Cook 2 to 3 minutes on each side or until no pink remains. Transfer to serving plates with pierogi and beans.
3. Drain fat from skillet. Add balsamic vinegar to hot skillet. Cook, uncovered, 1 minute or until reduced by half. Drizzle over pork, pierogi, and beans. Sprinkle with chopped rosemary. Serves 4