Cook the rigatoni according to packet directions until al dente. Meanwhile, in a separate saucepan, boil the chicken breasts until fully cooked.
In a large bowl, combine the soup, mayonnaise, lemon juice, curry powder, green beans and mushrooms. Drain and stir in the rigatoni. Cube the cooked chicken breasts and stir this in as well. Transfer this mixture to a baking dish.
Sprinkle the cheese on top. In a medium bowl, combine the butter and the corn flakes then spread this mixture over the cheese. Sprinkle with the parsley.
Bake in preheated oven for 20 to 30 minutes, until the cheese is bubbly.