Cook the kohlrabi and potatoes in salted water until cooked. Fry the ham. Preheat the oven to 200 ° C. Whisk the cream, salt, pepper and nutmeg together. Layer the kohlrabi, potatoes and boiled ham in a baking dish and pour the cream sauce over them. Scatter cheese on top. Baked in the oven for about 20 minutes.