Wash, peel and coarsely dice the potatoes. Wash marjoram, dab dry and chop except for something to garnish. Boil the potatoes and marjoram in a little salted water, cover and cook for 20 minutes.
Meanwhile wash and peel the cucumbers, cut them in half lengthwise and scrape out the seeds with a spoon. Cut two halves into cubes. Peel, wash and finely dice the carrots. Peel and finely dice the onion.
Heat 10 grams of fat in a saucepan and fry the onion in it until transparent. Add cucumber and carrot cubes, sauté and deglaze with stock and lemon juice. Place the cucumber halves in the stock, cover and cook for 15 to 20 minutes.
Roast the sunflower seeds in a dry pan. Warm the milk. Drain the potatoes, add hot milk and mash the potatoes. Season to taste with salt, pepper and nutmeg. Spread the mashed potatoes into the cucumber halves and arrange on plates with the stew.
Foam the remaining fat in a saucepan and pour over the puree. Sprinkle with sunflower seeds. Serve garnished with marjoram.