Peel the kohlrabi and cut into slices. Boil milk with one eighth liter of water and salt. Stew kohlrabi for 10 minutes, remove and drain.
Cut ham into cubes. In a greased gratin dish alternate ham and kohlrabi form.
Melt fat in a frying pan. Sauté flour in it, add cooking broth while stirring and let it bubble up. Season to taste with salt and pepper and a pinch of nutmeg and add the egg yolk.
Immediately pour over the casserole form. Sprinkle with cheese. Bake at 200 °C for about
15 minutes.
Tip: It is best to use your favorite ham – then your dish tastes twice as good!