Mix together the warm water, margarine, salt and milk powder. Slowly stir the flour into the liquid ingredients until it makes a soft dough. Spray a medium-sized bowl with vegetable oil spray and place the dough in the bowl. Spray the top of the dough with vegetable oil spray. Cover and let rise in a warm place until double in size.
Divide the dough into 12 equal pieces. Let the dough rest for 5 - 10 minutes. Prepare filling by mixing all ingredients and stirring well. Roll out each piece of dough and put a couple of spoonfuls of filling in the middle of the dough. Add a little sour cream and roll the dough up like little loaves of bread.
Let the loaves rise until double in size. Bake at 350 degrees for 20 - 30 minutes. They should be golden brown. Place on a wire rack and brush a little margarine on top of each little loaf.
In a small skillet heat 1 1/2 Tbsp oil and saute onion a few minutes. Serve onion on top of the potato pies with a dollop of sour cream.