German Potato Casserole

7 large Idaho baking potatoes3 tablespoons water3 large sweet onions, sliced7 tablespoons butter, divided14 ounces Gouda cheese, sliced3 cups heavy whipping creamSalt to tasteBlack pepper to tastePlace potatoes in cold water. Bring to a boil and cook until about three-quarters cooked through, 25-30 minutes. Let potatoes cool about 10 minutes; peel and slice.On low heat in large skillet add water and onion and cook about 30-40 minutes or until very tender. Then add 3 tablespoons butter and cook until onions are caramelized, 5-10 minutes more. Heat oven to 350 degrees. Spray a 9-by-13-inch baking pan with nonstick spray. To assemble: Set aside enough potatoes and cheese for a thin top layer. Then, layer half of the remaining potatoes in pan, half the cheese and half the onions. Dot with 2 tablespoons butter. Season with salt and pepper. Repeat layers one more time then top casserole with reserved potatoes and cheese. Pour the heavy cream over the entire dish until the cream comes close to covering most of the dish. You might not use all the cream. Bake about 45 minutes or until bubbly. Cover with foil if dish is getting too brown.Serves eight to 10.Cook's note: Dish can be made the day before and refrigerated.Nutrition values per serving: 584 calories, 46 g fat (28 g saturated), 32 g carbohydrates, 2 g fiber, 14 g protein, 165 mg cholesterol, 1,058 mg sodium.