Fischbrötchen: German Cod Sandwiches

Boil one egg until hard and peel while running cold water over it. Finely dice with some cornichons (I used 4 small cornichons). Remove core and finely dice half the apple. Combine mayo, yogurt, pickle juice, lemon juice and season to taste with salt and pepper. Chop the parsley and stir in.
Whisk the egg with some milk and salt and transfer to a deep plate or shallow bowl. Pour some flour and some breadcrumbs onto two separate plates. Dust the fish in flour, then coat in the egg mixture and finally coat in the breadcrumbs. Heat butter in a skillet over medium heat and cook the fish for 4 to 5 minutes on each side. Transfer to a clean plate covered in paper towel.
Half the rolls and lightly toast them in the skillet or in a toaster. Add some lettuce to the bottom of the roll, then add the fish, then the remoulade sauce and close the sandwich with the second half of the roll. Serve the remaining remoulade sauce on the side.