Peel the onions. Cut half into rings, dice the rest. Cut two gherkins into slices, dice the rest finely. Cut beetroot into slices as well. Coarsely chop the corned beef.
Melt the fat. Fry onion dices and corned beef in it. Add 100 ml water and milk, bring to the boil briefly and remove the pot from the heat. Stir in the purée flakes. Stir in the cornichon cubes.
Season to taste with salt and pepper. Wash the chives, dab dry and cut into small rolls. Arrange the lobskaus with prepared onion rings, cornichons and red beetroot slices, roll cups and chive rolls.
Serve garnished with dill and lemon.