Combine fish, potatoes, herbs, gherkins, peppercorns and salt in a bowl. Mix well and divide the mixture into four equal portions and shape them into patties.
Brush a little oil on top of each patty and set aside. Heat the Grill Pan. Halve burger buns and place them on it. Cook till light golden and crisp. Set aside.
On the same hot pan, cook the patties, turning sides, till evenly cooked on both the sides. To serve, place the base of the bun on the plate. Apply cream cheese, top with some lettuce leaves and gherkins.
Place the hot patties on top and close with the other half of the bun. Serve immediately.