Clean and wash the cucumber and cut into fine slices. Mix vinegar with salt, pepper and sugar. Whip oil into it. Wash, clean, halve, seed and cut tomatoes into small cubes.
Mix the tomato cubes and vinaigrette with the cucumber slices and allow to soak. Bring 1/2 litre water and 1/2 teaspoon salt to the boil. Remove the pan from the heat, add milk and fat. Stir in the puree powder and let the puree swell for 1 minute.
Wash the herbs, dab dry and chop coarsely, except for some parsley for garnishing. Stir the chopped herbs and horseradish into the mashed potatoes, season with salt and pepper. Arrange the horseradish-herb puree with the cucumber salad and the smoked pork loin on plates.
Sprinkle Kasseler with coarse pepper and serve plate garnished with the remaining parsley.