Sweet potatoes when they get older can suddenly without warning go wrotten very quickly therefore it is worth keeping an eye on them and if they start to discolour deal with them quickly by preparing them for the freezer. That way you won't waste precious ingredients. All I do is peel them chop them into cubes, blanch in boiling water, for 2 minutes, straight into cold water, drain and dry off and package in either freezer bags or little plastic boxes and pop into your deep freeze. I usually cooksweet potato in the oven in oil with Rosemary - roasted but you can use it in stews etc, or mash it with a little cream and butter. Its a good all round vegetable that appears regularly on my repertoire. We are very fond of roots of any description. Plus its alwayts handy to have vegetables of any description to hand and it makes sure none of the fresh vegetables I buy each week go to waste an important crtiteria in this day and age. You can do the same with carrots and parsnips too.