Place Kassler on aluminum foil coated with oil, close the foil and place the packet in the preheated oven. Cook for about 60 to 50 minutes.
Mix the mustard with the honey.
Open the foil 15 minutes before the end of the cooking time, cut into the Kasseler four times, spread the mustard-honey mixture and stick a pineapple slice in each incision. Close the foil again and finish cooking.
Arrange on a preheated platter and serve with potato croquettes and lettuce.