1. Peel and dice the potatoes and kohlrabi. Peel and finely chop the onion and garlic. Add the oil to a large pot and heat up. Add the chopped onions and garlic and fry until glossy. Add the potatoes and kohlrabi and fry briefly. Add the mustard, mix everything well, and fry for about 1 minute more. Deglaze with the vegetable stock and heavy cream. Bring everything to a boil, then add the sausages, reduce the heat and let simmer for about 20-25 minutes. Mash/puree a small portion of the potatoes and kohlrabi with a potato masher or immersion blender and season with salt, pepper, and chili flakes before serving.