Boil sweet potatoes until fork tender. Once cool, peel skin.
Separately combine (approximately):
1/2 cube butter
1/2 cup brown sugar
1/2 cup fresh-squeezed orange juice
Bring to a boil. Pour over cut up sweet potatoes in a 9 x 13 pan. Sprinkle with nutmeg. Bake at 350 until warmed through.
Updated recipe notes from Mom on 11/18/20.
That recipe would make a 9 x 13 pan, which I'm sure none of you would want that much. I think it also has too much butter and brown sugar.
For a smaller pan, I would probably do 4 large-sized yams (if they are too small they won't cut into nice pieces). Try to get them the same size, so they all cook about the same time. Don't overcook so they are mushy.
After they have cooled, peel and cut them into fairly large circles or chunks. This is where the guessing game comes in. I would probably do around 1/4 cup brown sugar and 1/4 cup butter and fresh-squeezed orange juice until it makes the thickness you want. Cook the butter and sugar until they are combined and then add the orange juice. Sprinkle with nutmeg. (You can add more brown sugar and butter if you want it sweeter).
You just have to look at it and see if it looks like enough to cover your yams. I butter the dish, so that is also adding extra butter when it cooks.
Bake at 350 for about 30 minutes.
You can make these the day ahead and just reheat. If you're going to make ahead and reheat I would only cook them for about 20 minutes.