1. Slice or shave the fresh fennel into thin slivers and add them to a large mixing bowl together with the yogurt.
2. Stir and season with a pinch of pepper and salt. Then add the freshly chopped parsley, the horseradish, the lemon juice and pink pepper.
3. Stir the fennel salad again. Check the seasoning and add extra pepper, salt, horseradish or lemon juice to taste if necessary. Toast the (sourdough) bread slices. Let them cool a little and then top them with some arugula. Season with a little pinch of pepper.
4. Place some of the fennel salad on top of it.
5. Now top with a few slices of the roast beef. Finish with a last sprinkle of freshly ground pepper and close the sandwich with another slice of the toasted bread. Serve immediately.