HEAT oven to 375ºF.
MICROWAVE potatoes in small microwaveable bowl on HIGH 4 min. or until tender. Mash until smooth. Add cream cheese; mix well.
BROWN meat with mushrooms and onions in dressing in large skillet; drain. Mix flour and water. Add to meat mixture; cook 2 min. or until slightly thickened, stirring constantly. Stir in beans; spoon into 2 (2-cup) ramekins sprayed with cooking spray. Cover with potato mixture.
BAKE 15 min. or until casseroles are lightly browned and heated through.