Wash the cress, shake dry and cut from the bed. Mix quark, sour cream and 1 tablespoon lemon juice. Season to taste with salt, pepper and sugar. Stir half of the cress into it
Cut avocado in half lengthwise, stone and peel. Cut avocado halves lengthwise into about 12 slices and immediately sprinkle with remaining lemon juice.
Arrange salmon ham and avocado slices each with a little cress cream on 4 plates. Sprinkle with the remaining cress. Serve with fresh white bread