I read that you can steam or boil the leaves for 3-5 minutes or a tad more. Drain the water, well(if boiled) and mix with some Sesame oil and Soy sauce. Then sprinkle with toasted Sesame seeds and salt or some Japanese sprinkle called, "Sishimi" that has sesame seeds, I think salt and seaweed bits.
Since I was not going to eat the leaves right away I dehydrated the leaves and not the stems at 135 until crisp and stored them in a glass jar. Good for adding to soup and stews in the winter.
As you can see, I left the little baby leaves on. They are good. Kohlrabi itself has an interesting taste and the Lemon juice makes the flavor much better. I ate 2 bulbs and the energy it gave me was intense for the small amount eaten. Kohlrabi has more nutrients and energy than calories. A plus in my book. I see it as, "Oh that means I can eat more." : )
I have sprouted more and will grow more for the fall and winter. They can handle freeze after they have been established or I assume hardened off as they say in garden talk.
You can eat these raw by themselves or with oil, salt and optional lemon juice. Or added to salads. I am sure the same goes for the leaves. You could also dry the leaves at a temp. between 100-115 to keep them raw to.