Peel and chop the onions. Heat the lard. Brown the onions in it. Add sauerkraut and bay leaf. Season with pepper. Let it braise for 15 minutes at high heat. Meanwhile bring 1/2 litre of water to the boil.
Season with salt. Remove the pot from the heat. Add milk. Stir in the puree flakes briefly, allow to swell for about a minute. Wash and chop the parsley and fold into the puree. Pour into an ovenproof dish.
Cut cabanossi into thin slices. Mix with the sauerkraut and add to the puree. For the crust mix mustard, egg yolk, crème fraîche and peppercorns. Spread on the sauerkraut. Bake in the preheated oven (electric cooker: 225 ° C/ gas: level 4) for ten minutes.
Serve garnished with parsley.