Clean, wash and drain the lamb's lettuce well. Also drain mixed pickles. Spread slices of bread with the horseradish cream. Remove the skin from the mackerel fillets.
Cut the fillets into diagonal strips about 3 cm wide. Halve bread slices and cover the halves with the mackerel strips. Wash lemon hot. Cut one half into narrow slices, from the 2.
Squeeze half the juice. Mix 3 tablespoons lemon juice, 2 tablespoons water and oil. Season the lemon marinade with salt, pepper and sugar and mix with the lamb's lettuce. Arrange 2 bread halves, some salad and mixed pickles on 4 plates.
Serve garnished with the lemon wedges.