Wash and scrub the sweet potato and stab it with a fork a few times before shoving it into the oven. If you don't have prepackaged shelled chestnuts, you'll have to bake the raw ones in their shells with a layer of water in the pan first. It's just easier to get a ready-made bag if you ask me.
Anyway, wait 'till the potato is done. Cut it open, let it cool a bit. Peel the skin off if you want, or you can cut it up and toss it into the mash. Add the margarine sugar and spices, mash until blended. Cut up the chestnuts and add them in along with the cranberries. Mix well and serve warm as a side dish or use it as a stuffing for poultry or wrapped with a pork chop or fish fillet. Mmm, yummy.
To feed a family of four, double the recipe. And if you're not having anything else with it, this could be just one serving. If you find a way to tweek this and make it better, let me know!