Heat oil in a frying pan over medium heat.
Sauté onion in hot oil until translucent.
Now add chicken and cook for 2 minutes.
Now add the sour cream, mayonnaise, black pepper, salt and tomato ketchup.
Sour cream and mayonnaise will release water, but if the mixture is dry add about a 1/4 cup water so the flavors get a chance to blend.
Cover the lid and cook for 10 minutes or until all water dries up.
Preheat oven at 350 degree F or 170 degree C.
Roll the puff pastry and cut into rounds by using a round cookie cutter.
Sandwich chicken filling between two round pieces of puff pastry.
To seal the edges use water. and press with fork around the edges.
Brush the tops of the patties with egg wash.
Bake in the preheated oven for 15-18 minutes or until the pastry is puffed and the tops are golden brown.
Remove from the oven. Chicken Patties are ready to serve. ENJOY!