Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13 inch baking dish.
In the prepared dish, make a single layer of sweet potato slices. Place a few onion slices on top, dot with butter, and sprinkle with salt and pepper. Repeat, alternating layers of white and sweet potatoes.
In a small bowl, or measuring cup, combine flour and broth. Pour over potatoes.
Sprinkle cheese, bread crumbs and parsley over the potatoes. Dot with remaining butter. Cover.
Bake in preheated oven for 1 hour, or until potatoes and onions are soft.