Baked yams:
We use red jewel yams (they are not identical to sweet potatoes.) They have dark red skins. To choose the most flavorful ones, run your fingernail along them in the store. Is the flesh underneath orange? Good. Yellow? Not so good, but okay.
Wash them and prick each twice with a fork. Place on a foil-lined baking sheet or in a foil-lined baking dish. Trust me on the foil-lined part. They can leak sticky goop. No need to oil anything.
Bake at 450 for at least an hour, no matter how thick they are. After that you may have to remove some and leave others in. Test for doneness with a fork. It should slide in very easily.
To eat: We are messy eaters, so we just break them in half and scoop out the insides with a spoon. You can also scoop out the insides and mash them a little so you can eat them without the mess!
Once you've scooped out the insides you can do things to them. Adding fats (butter) or sweetener defeats the whole purpose of baking them whole, because baking them whole in that way makes them naturally very sweet. So if you're going to mash them up with stuff, do it in a way that makes them more interesting, like using the kind of spices you use for pumpkin pie, or adding pineapple, or even yogurt. I make yam pie -- like pumpkin pie, but with no crust. I'll post the recipe later.
DO NOT WRAP THEM IN FOIL. Trust me -- the insides will be watery and not nearly as sweet or flavorful. This is the HUGE mistake made by restaurants, whether they are offering whole baked sweet potatoes or whole baked yams. That's why they offer their baked sweet potatoes with butter and brown sugar. Their finished product is always watery and bland.