Preheat oven to 375 F.
Lightly coat 9-by-13-inch baking dish with nonstick cooking spray.
Spread German potato salad evenly in dish. Top evenly with chicken.
In small bowl, stir heavy cream, salt and pepper. Pour mixture over chicken.
Sprinkle with cheese, bacon and onions, if desired.
Bake 15 minutes, or until casserole is bubbly. Let stand 10 minutes. Top with additional onions, if desired.