Peel the onion, kohlrabi and carrots and cut into small cubes. Put the tomato paste, oil, ginger and bay leaves in a large saucepan and mix well. Let it steep for about 1 hour.
Briefly sweat the marinated ingredients over high heat. Add the water, season with salt and boil for 10 minutes at a bubbly rate.
In the meantime, peel the potatoes and grate them finely. Mix in the grated potatoes and cook over medium heat for 30 minutes. Stir occasionally.
Wiener sausages or meat sausages go well with it. Without sausage, the soup is vegan and tastes delicious.