Sprinkle pork with 1/4 teaspoon salt and 1/8 teaspoon pepper. Heat the oil in a large nonstick skillet over medium-high heat. Add pork; sauté 5 minutes on each side or until golden. Remove pork from pan. Add onion and mushrooms to pan; sauté for 3 minutes. Carefully add whiskey to pan; cook for 1 minute or until liquid almost evaporates. Stir sour cream mixture into pan. Return pork to pan; spoon sauce over pork.
Wrap handle of skillet with foil. Cover and bake at 300° for 1 hour. Serve immediately.