Heat oven to 350°F. In 12-inch nonstick skillet, cook chicken and onions, stirring occasionally, until chicken is browned and no longer pink in center.
Stir in remaining filling ingredients. Spoon into ungreased 8-inch square (2-quart) glass baking dish.
In 2-quart saucepan, heat water to boiling. Remove from heat. Stir in remaining topping ingredients except paprika. Spoon topping over chicken mixture; sprinkle with paprika.
Bake uncovered 25 to 30 minutes or until bubbly.