Line a large baking tray with paper. Lay out the pastry sheets, overlapping slightly and press to seal together.
In a large pan, heat oil on medium heat and add chicken. Cook for 10 minutes, turning often. Add leeks, mushrooms and kransky, continue cooking until leek is very soft and chicken is cooked in middle. Add drained potatoes, season with salt & pepper to taste.
Using a spoon, spread filling mixture over the middle area of the pastry. Fold and pinch the pastry up on all sides to form a crust. Add a little of the pan juice.
Drizzle a little cream evenly over the filling and sprinkle with cheese. The pie can now be frozen if desired.