Preheat the oven to 200 °C. Bake the potatoes in the oven on a bed of sea salt [1] for about thirty minutes until cooked.
Scrape the potatoes from the skin and press them. Mix with egg yolk and potato starch (adjust mass!) until dough is dry and smooth. Season with salt and pepper. Possibly cook some test gnocchi first! Form rolls of the dough with a diameter of two centimeters, cut gnocchi three centimeters long and form grooves with a fork. Cook the gnocchi in simmering salted water until they rise to the surface. Remove and drain [2].
Rinse the vegetables, clean them and remove the peel. Cut carrots into slices, kohlrabi and parsnips into sticks. Place vegetables in a saucepan with rapeseed oil, sauté briefly, extinguish with vegetable soup and steam until soft with lid closed. Stir repeatedly.
Finally, season strongly with salt and freshly ground pepper, and fold in the whipped cream and the freshly finely chopped parsley leaves.
In the meantime, melt a little butter in a frying pan and toss the gnocchi in it.
Serve the vegetable sauce with the gnocchi.
[1] Causes the cooked potatoes to contain much less moisture.
[2] The gnocchi can easily be cooked a little in advance.