How to Make It
Place potatoes in a large saucepan; cover with cold water. Bring to a boil. Reduce heat, and simmer 20 minutes or until tender; drain and cool.
Combine mayonnaise, yogurt, green onions, horseradish, vinegar, 1/4 teaspoon salt, and 1/4 teaspoon pepper in a medium bowl. Stir in potatoes. Gently fold in radishes and eggs.
Heat a grill pan over medium-high heat. Sprinkle pork medallions with remaining 1/4 teaspoon salt and 1/4 teaspoon pepper. Spread garlic evenly over pork. Lightly coat pan with cooking spray. Add pork; grill 4 minutes on each side or until desired degree of doneness. Let stand 5 minutes before serving. Serve with the potato salad.