I learned the hard way that these are in fact something you should make and then cook immediately. I shredded my potatoes too early and they ended up grey.
Having said that, they actually tasted great (even for being grey (I had a bad experience with grey soup once so I was apprehensive)) and it was a great way to hide veggies. If you have picky kids...or a picky husband (like me)...this was an excellent way to get in some much needed veg. You can put in whatever you like, but I used onion, zucchini and bell peppers.
This recipe also makes a huge amount but it should halve or quarter easily.