Mash the cooked potatoes and mix thoroughly with the steamed cabbage and cream.
Season the mixture well with salt and black pepper.
Fry the sliced onion in the fat over moderate heat until soft and browning.
Press half the potato mixture in an even layer over the onions.
Fry for 5 minutes until the bottom is well browned and crispy.
Cut the mixture into quarters and turn them over carefully.
Press the remaining mixture on top and fry for several more minutes.
Turn the mixture again until all layers are browned and crispy.