I grew them in an old compost bag turned inside out so that the black was on the outside. You need to put 3 in the compost then cover with more compost and when they start to sprout put in 3 more and keep earthing up so that the spuds stay in the dark and don't go green. You could put in another layer of 3 spuds but probably no more.

Sorry missed the 'sweet' part of your question. I have only grown ordinary spuds before.