Place a piece of parchment paper on a large cookie sheet. Spray a little oil on the parchment. Set aside.
Prepare 2 1/2 cups mashed potatoes.
DOUGH.
Beat together 1 cup of the mashed potatoes, the 1 tablespoons of oil and the salt. Add the flour, and baking powder, mix well.
Mix in the water and knead into a smooth dough. I used my mix master to mix this and it worked great. The dough was wonderfully soft.
Let the dough rest in a bowl covered with a damp cloth for about 1/2 hour.
FILLING.
Saute the onions in the tablespoons of oil until transparent. Mix in the rest of the ingredients. I mixed it with the mix master just until combined.
Cut the dough into 4 sections and roll each section out thin. Cut the circle into 4 more pieces and put 1-2 tablespoons of the filling in each.
Gather up the edges and join in the middle and pinch together so the filling doesn't leak out.
Put the knish on the parchment covered baking tray with the pinched side down.
Brush the top with soy creamer if desired.
Set the oven to 350'F and bake for 25 minutes until golden brown. Serve with horseradish or mustard.
Bon Appetit.
