I'm confused as well. I thought you were looking for a potato pancake that used grated potatoes in your previous thread. Are your leftover potatoes mashed? If yes, then the salmon mashed potatoes that your mom made makes sense. If they are boiled potatoes, than I'd make grated Kartoffel Puffer (which I linked to in your other thread on potato pancakes).
Perhaps the confusion stems from the various ways names by which potato pancakes are known:
Potato pancake - Wikipedia, the free encyclopedia
Or are you looking for a way to make potato cakes using leftover mashed potatoes? (My favorite way to use leftover mashed potatoes is to make lefse, but I would not call that a pancake, although it is flat and round like a pancake...).
We just shape the mashed potatoes and fry them in a hot skillet with butter...nothing fancy here. But you can added egg, etc.
Potato Cake Recipe - Allrecipes.com