For the potato pancakes, peel the potatoes and grate finely. Then squeeze and mix with egg yolk and flour. Season with salt and pepper.
Wash and finely chop the rocket. Mix cream cheese, horseradish and cream, season with salt and pepper and stir in a dash of lemon juice. Carefully mix in the chopped arugula. Bake the potato mixture in small cakes in hot oil until golden brown and serve the finished potato pancakes with the arugula horseradish sauce.