Line a large, flat salad bowl with arugula. Place the quartered and sliced apples on top and drizzle them immediately with a little apple cider vinegar.
Finely chop the shallots, coarsely chop the capers.
Mix the dressing with mustard, horseradish, salt, pepper, vinegar and walnut oil. Stir in shallots and capers. Spread the dressing over the salad and sprinkle the pine nuts over it.
Finally, drizzle the salad with pumpkin seed oil and maple syrup.