Drain mandarin oranges, reserving 2 tablespoons of the juice. Stir together reserved juice, sour cream, maple syrup, lemon juice, salt, pepper and hot pepper sauce. Set aside.
Place chicken, broth and garlic in large saucepan. Bring to a boil over medium-high heat; reduce to simmer. Cook until chicken is done, about 10 minutes, adding beans during last 5 minutes of cooking. Remove chicken to cutting board. When slightly cool, cut into strips.
Line four plates with lettuce. Gently toss chicken, beans and drained oranges with dressing. Place on top of lettuce; scatter chopped walnuts on top and serve.