Peel the onion and cut into strips. Heat 1 tablespoon of oil in a pan. Brown the onion in it. Add the sauerkraut, bay leaf, allspice, clove and 2 tablespoons of water, cover and braise over medium heat.
Wash the apple, grate dry and cut into small cubes. Mix mustard and flour in a saucepan and heat. Add cream and stock while stirring and simmer for about 2 minutes. Season the sauce with salt and pepper and remove from the heat.
Add diced apples to the sauerkraut. Wash and clean the leek and cut it into 24 approx. 1 cm thick rings. Peel white sausage and cut into 24 slices. Put 2 sausage and leek slices alternately on a skewer.
Heat 1 tablespoon of oil in a frying pan and fry the skewers in portions over medium heat for about 2 minutes on each side. Place the skewers on the sauerkraut and keep warm. Bring the sauce to the boil again.
Arrange 3 skewers, sauerkraut and sauce on each plate.