I made my own version of this with leftover jacket potatoes from Thursday & roast potatoes from yesterday & a cabbage/leek mix from the freezer for the DSes. It had a mixed reception - DS2 loved it & couldn't get enough, DS1 ate most of his with some persuasion 
Anyway, my question is, will the leftover mixture that I have not cooked keep in the fridge, or should I cook it first?
Thanks!