This potato side dish casserole has a rich creamy sauce. Try it at the holidays instead of mashed potatoes.
1. Heat butter and olive oil in a large skillet over medium heat. Add onions; cook slowly until browned, stirring occasionally, about 30 minutes.
2. Heat oven to 350 degrees F. In a large bowl, whisk together chicken broth, cream, flour, salt, and pepper. Stir in diced potatoes, cooked onions, and 1/2 cup cheese. Pour mixture into a 2-quart baking dish, and top with remaining 3/4 cup cheese. Cover with foil; bake 45 minutes. Remove foil, and bake 30 minutes more. Let cool; cover and refrigerate up to 3 days.
3. On Thanksgiving Day, remove potatoes from refrigerator and bring to room temperature. Heat oven to 375 degrees F. Heat in microwave for 20 minutes at 50 percent power to warm, then bake in oven for 20 minutes. Broil 3 minutes to brown top.