1. Wash chicken and pat dry. Place it in a pot of cold water (use enough to cover). Bring to a boil, reduce heat to a gentle boil and cook for 40 minutes. (Optionally, cook in a grill pan over medium-high heat, 5-7 minutes per side). Let cool and cut into small cubes.
2. In a large bowl, mix together chicken, chopped pickles, beans, cheese and mushrooms.
3. Refrigerate for about 30 minutes, top with mayonnaise, mix and serve.