Peel the potatoes and cook them in salted water. Peel, quarter and slice the kohlrabi, then cook in 500 ml vegetable stock for approx. 10 minutes until soft.
Remove the kohlrabi from the heat, add the milk and season to taste with the remaining ingredients (if you like it a little hotter, take the chili powder, otherwise you should leave it out). Put everything in a plate and serve.