In a medium skillet or pot, place chicken breasts side by side in water or broth. Make sure liquid completely covers chicken (1 inch above chicken is best). Bring water to a boil and then reduce to a simmer. Partly cover pot with lid and simmer for 12-15 minutes. Turn off heat and let chicken sit for an additional 15 minutes or until completely cooked through. Remove chicken from liquid and set aside. If you are tight on time, you can always use a store-bought rotisserie chicken.
While chicken is cooking prepare salad mixture. In a medium saucepan with steamer basket, bring one inch water to a boil. Add broccoli rabe, cover and steam for 3 to 5 minutes or until tender. Do not overcook. Let cool after steaming.
In a medium bowl, combine broccoli rabe, beans, avocado (optional), tomatoes, scallions and parsley.
In a small bowl whisk together olive oil, red wine vinegar, Dijon, salt and pepper. Pour over bean mixture and gently toss. Top with warm chicken and enjoy.