How many are in 3 lbs?
They make passable fries. Pretty much the same recipe you'd use to make regular potato fries in the oven. Also a puree, which would be similar to mashed potatoes. Boil them, and puree with whatever seasonings you want. May need to add some milk, cream or similar. I can't think of any other way I've used them other than roasting or in a stew which I think was suggested already.

Let us know if you discover any delicious uses for your 3 lbs!