Clean, wash and drain the salad and cut into strips. Peel and roughly dice the onion. Wash and quarter the tomatoes. Wash, clean and chop the peppers. Clean, wash and roughly grate the carrots.
Drain the tuna. Wash the cucumber, cut in half lengthwise and cut into pieces. Dice the toast. Peel garlic and press it through a garlic press. Heat the fat in a frying pan, add the bread cubes and garlic and fry until golden brown while turning.
Mix mayonnaise and yoghurt, season with salt, pepper and horseradish. Stir in ketchup and season with sugar. Wash the chives, dab dry and cut into small rolls. Mix lettuce, 3/4 of the onion, tomatoes, peppers, 3/4 of the carrots, cucumber and tuna and serve with a dash of horseradish mayonnaise.
Serve sprinkled with chives, remaining onion and remaining carrot. Add the remaining horseradish mayonnaise and garlic croutons separately.