Peel the kohlrabi, cut away the woody parts, halve, cut into thin wedges (or small cubes).
Cover with salted water in a saucepan, cook until crisp, strain, prepare the brew.
Melt the butter in a casserole roll, roast the finely chopped onion in it until colorless, stir in the flour, sweat briefly and add a little kohlrabi sauce, stir until smooth with a whisk.
Stir in the kohlrabi, cook for a few minutes, stir in the sour cream and parsley with salt and pepper.
just like that with bot or as a vegetable side dish.