Preheat a convection oven to 180°C (approximately 350°F).
Peel the kohlrabi root. Remove the greens and chop. Slice the root into 0.7 cm (approximately 1/4 inch) slices. Lay kohrabi slices in a buttered casserole dish so that they overlap. Reserve the leaves for later.
Mix the cream with the crème fraîche and eggs. Season with salt, pepper and nutmeg to taste. Pour the sauce over the kohlrabi. Sprinkle the casserole with the kohlrabi greens and the cheese. Bake until the kohlrabi is tender and the sauce is bubbling, about 25-30 minutes. Season with pepper to taste.