To make this salad even quicker to prepare, just use a bag of salad greens that are already washed, chopped and ready to go. Toast the walnuts in the skillet (without oil) before cooking the mushrooms if you like. It will bring out more flavour in the walnuts.
Divide the greens evenly in each bowl or plate. Set aside.
In a large skillet or wok over high heat add 2 tbsp. olive oil. Add the mushrooms and sauté until golden and softened, about 1 minute. Remove mushrooms from pan and set aside.
In the same skillet over high heat, add the remaining 3 tbsp. of olive oil. Add chicken, shallots, garlic and rosemary. Season the mixture with salt and pepper. Sauté until chicken is lightly golden and looses its pinkness. Add the beans and mushrooms and sauté for 30 seconds to 1 minute. Add wine and heat through, about 30 seconds. Remove from heat. Add the vinegar. (Note if the green beans sit in the cooking liquid too long they will loose their green colour from the acidity in the wine and vinegar.)
Top each bowl of greens evenly with chicken mixture and the pan juices. Sprinkle with walnuts. Serve immediately.