As far as I know it's only known in the Rhineland, Westfalia (both regoin in the very west of germany) and some parts of netherland.
It has a very subtile taste. It's very fresh and watery and reminds of daikon radish but lighter.
I think it would be great served raw in a salad but the most common and traditional way of preparation is to cook a stew with starchy potatoes, which is called "Durcheinander".
Stielmus, which is also called Rübstiel is one of the ancient, local vegetables, that is nearnly forgotten and it's even seems to get more unknown from year to year.
When I was a child it was available at most of the markets in my hometown Düsseldorf, which is the capital of the region and the state of Northrhine-Westfalia.
Nowadays it's hard to find and you have to go to a farmers market, a healt food store or a very well stock greengrocer at the market.
Last staturday I took out my kids for a little walk and went to the most famous greengrocer at the bigest market of the town called "Schier".
They have all the fruits and vegetables, you can imagine, the quality is out of the world and the prices are as high as nowhere else, but they seemed to be the only greengrocer carryin "Stielmus". That made me said because it's a really big market.
The stielmus was expensive, up to 4 € for two bunches of it with a waight of a bit more than one pound. That's really pricey for the greens of a turnip but the quality was out of this world. I and my two year old son began to snack the smallest and lightest little greens of it. He even learned the word "Stielmus" and wanted more and more.
Yesterday a went to the organic food store and looked for Stielmus but the price was even higher and it seemed to have lost most of its freshness.
If you want to cook it at home and can't get Stielmus, which should be the case for most of you, you could maybe try to cook it with chicoree, chard, or the greens of other root vegetables.
500 g of Stielmus, washed and chopped (throw away the biggest leafes because they are bitter and your aiming at the stalks)
500 g of starchy potatoes, peeled and roughly cubed
1 1/2 cups of vegetable stock
4 tbs of margarine
1 tsp of mustard
2/3 cup of unsweetened soy milk or cream or any other non-dairy milk
1/2 cup of white wine (optional)
salt and pepper for seasoning
1. Put the potatoes, stielmus and stock into a pot.
2. Bring to a boil, reduce heat to medium and simmer until the potatoes get mashy. (about 25 minutes)
3. If there's a lot of stock remaining try to put it away.
4. Mash with a potato masher.
5. Season with mustard, salt, pepper, soymilk and wine.
The result should be like a liquid form of mashed potatoes, where you can stil reconginze pieces of the potatoes and the stielmus. Maybe some kind of potatoe risotto.
Enjoy as it is or as a side dish with fried tempeh, chickpea-cutlets or any other fake meats.