Easter Egg Casserole

Tonight I made a recipe called "Easter Egg Casserole" from the cookbook "Family Feasts for $75 a Week" by Mary Ostyn. The recipe called for making a white sauce of sauteed onions, butter, flour, and milk and then adding the sour cream at the end, then pouring it over diced sweet potatoes and regular potatoes and ham and adding some cheese on top. It was absolutely awful. I think the sour cream broke down while it was baking because the casserole came out watery and the sour cream mixture had separated. AWFUL, just awful. This is the first recipe I've tried from the book and there are a few others I am interested in trying.