Use a spoon to remove the seeds from the cucumber. The seeds may make the salad too watery and thin.
Chop the cucumber, apple and shallot in small cubes and add those to a bowl.
Tear the fish fillets apart and add them to the bowl as well. By rubbing the fish in between your fingers, you can check directly if the fish still contains any bones (and remove those).
The Salad
Then add the quark, mayonaise, horseradish and grated zest of a lemon. Mix-up everything and season with salt & pepper. Feel free to add more quark and mayonaise to make a smoother salad. Love to spicy things up? Add more horseradish to your taste!
Serve on toast with sliced radishes and microgreens / cress.