1. Peel the kohlrabi, making sure to remove the fibrous layer just under the skin, and cut into 1/2-inch dice. If there are greens attached, wash, stem and blanch them for 1 minute in salted boiling water. Transfer to a bowl of cold water, drain, squeeze out water and chop coarsely. Set aside.
2. Put your stock or broth into a saucepan and bring it to a simmer over medium heat, with a ladle nearby or in the pot. Make sure that it is well seasoned. Turn the heat down to low.
3. Heat the olive oil over medium heat in a wide, heavy nonstick skillet or a wide, heavy saucepan. Add the onion and a pinch of salt, and cook gently until it is just tender, about 3 minutes. Do not brown. Add the diced kohlrabi and the garlic and cook, stirring, until the kohlrabi is crisp-tender, about 5 minutes.
4. Add the rice and stir until the grains separate and begin to crackle. Add the wine and stir until it has evaporated and been absorbed by the rice. Begin adding the simmering stock, a couple of ladlefuls (about 1/2 cup) at a time. The stock should just cover the rice, and should be bubbling, not too slowly but not too quickly. Cook, stirring often, until it is just about absorbed. Add another ladleful or two of the stock and continue to cook in this fashion, adding more stock and stirring when the rice is almost dry. You do not have to stir constantly, but stir often. After 15 minutes, stir in the greens from the kohlrabi. When the rice is just tender all the way through but still chewy, in 20 to 25 minutes, it is done. Taste now, add pepper and adjust salt.
5. Add another ladleful of stock to the rice. Stir in the Parmesan and the parsley and remove from the heat. The mixture should be creamy (add more stock if it isn't). Serve right away in wide soup bowls or on plates, spreading the risotto in a thin layer rather than a mound.
Yield: 4 to 6 servings.