For the clear red cabbage soup with butter semolina gnocchi, first boil the red cabbage strips in the vegetable stock for 15 minutes, then strain through a sieve and pour the juice into a pot.
Peel the root vegetables and chop them with the leek in a blender. Whisk in the well-chilled egg whites and mix with the vegetables. Stir into the still-warm soup while heating slowly. The soup should not boil. The heat will cause the egg whites to set, forming a “cake”. Remove the cake, season the soup with port wine, salt and lemon juice (the lemon juice will also change the color from blue to red).
For the semolina dumplings, heat butter with semolina and milk in a saucepan and stir while heating slowly. Season to taste with salt, pepper and nutmeg. When the semolina porridge is firm, remove from heat, add beaten egg and yolk, mixing very quickly.
Put a pot of salted water and form dumplings with two spoons. Put them into the salted water, making sure that the water is at boiling point (should not boil strongly). When the semolina dumplings float to the surface (after about 10 minutes), remove and serve clear red cabbage soup with butter semolina dumplings.