Bring a pot of salted water to a boil. Meanwhile, remove the leaves and peel the kohlrabi. Cut off the hard part of the stem. Cut the kohlrabies in half*. Cook in boiling water for about 30 minutes or until cooked through, but still firm to the bite. Do not overcook them. Remove the kohlrabi halves from the water and let cool.
In the meantime, mix all ingredients, except 2 tablespoons of Mozzarella, in a small bowl. Scoop the flesh from the kohlrabi halves until they resemble nests. Finely chop the flesh and add to the cheese mixture. Fill hollowed out kohlrabi halves with cheese stuffing. Sprinkle the stuffed kohlrabies with remaining Mozzarella.
Bake the kohlrabies in a greased baking dish on 350 degrees Fahrenheit until the stuffing is golden brown and heated through, about 20-30 minutes.
Sprinkle with Parmesan and fresh dill, if desired.
*If your kohlrabi bulbs are small, cut off the tops instead of halving them, otherwise the "nests" might be too shallow.