Potatoes Gratin. Scalloped Potatoes. Call them what you will, they're oven-baked sliced potatoes in a dairy mixture. You can omit the sweet potatoes but you'll miss both a flavor enhancement and attractive color. Likewise, you can omit the black olives but they do add both flavor and color. I've not added ham to the ingredient list; add some chopped ham or bacon if you wish.
Potatoes. Red or white 'waxy' potatoes provide a firmer result; white potatoes such as Russets give a softer texture. For in-between, Yukon Golds are great. Peel, then slice thinly (about 1/8").
Sweet potatoes. Peel and slice just like regular potatoes. But beware—once the peel is removed, sweet potatoes blacken quickly as they're exposed to air. Solution: Peel, slice and put the pieces in a bowl of cold water until you're ready to use them (do the same with the regular potatoes).
Cheese. Cheddar cheese works fine. For heightened flavor, Gruyère is excellent (or half cheddar and half Gruyère). Or use crumbled blue cheese (but cut quantity in half).
Bread crumbs. Use plain, unseasoned crumbs (Progresso brand is a very good choice). Crumbs are better if you toast them first. Bring a dry skillet to medium-high heat, add crumbs to about 1/4" deep, then toast until browned while shaking the pan frequently to avoid burning.
Milk. At a minimum, use whole milk. Half-and-half is the liquid of choice; besides better taste, it has less tendency to turn the potatoes mushy. Use from one to 1-1/2 cups—one cup will produce a thicker, drier dish. It's not absolutely necessary, but it's a good idea to heat the milk in a microwave before pouring it over the layered potato mixture.
Baking dish. I prefer a shallow (about 2") baking dish roughly 7x11". The recipe may require more than one baking dish, depending upon the size of potatoes used. First coat the baking dish with a thin layer of butter. Then make about three layers of ingredients, each layer made up of potatoes, sweet potatoes, onions, cheese, bread crumbs, olives, bits of butter, paprika, and salt and pepper.
Baking. Bake on your oven's center rack, the dish covered loosely with foil. When the dish is done, remove the foil and turn on the oven's broiler element for 3-4 minutes to brown the top. Remove the dish and let it rest for a few minutes before serving. If you're a dill lover, sprinkle a little chopped dill leaf on the finished dish.
