Preheat the oven to 400° F.
Slice the chicken into strips. Peel the onions and finely mince. Heat the olive oil in a pan and add the chicken strips and minced onions. Sautee over medium heat about 5 min, while stirring.
Pour the contents of the pan into a dish and sprinkle with parsley. Add and arrange the roundly cut potatoes.
Cut the Roquefort into strips and sprinkle over the potatoes. Bake in the oven for about 12 min.
During this time, wash and drain the mesclun. Pour into a salad bowl. Peel, chop and add the shallot. In a separate bowl, mix the lemon juice, yogurt and 1 tbsp. of water. Salt and pepper. Pour over the salad.
When the casserole is ready, serve immediately with the mesclun salad.