1. Place potatoes in a large, heavy-bottomed pan and cover with water. Bring to a boil and cook until tender (20-25 minutes).
2. Drain and rinse with cold water. Let cool until comfortable to handle (15-20 minutes). Cut into bite-sized pieces.
3. Whisk together lemon juice, oil, salt, and pepper in a large bowl. Add the potatoes and toss to coat.
4. Just before serving, add scallions and mint to the salad and toss gently.