Never tried kohlrabi, but regular turnips are delicious cooked in beef broth and served with plenty of hot sauce.
Unless you are Jewish, you should try cooking them with fatback. And chopped up with the greens.
Turnips work pretty well mashed like potatoes. A little sour cream, a little dairy butter, a little horseradish. Throw some fresh grated parmesan on top, makes a nice side out of an unloved, fairly cheap vegetable that keeps well.
I like kohlrabi, but regular turnips kind of get me right in the back of my throat...makes it start to close up and I have a hard time swallowing.
Lots of sour cream is the only way I’ve managed to overcome this problem. Maybe hot sauce is a better route.