Generously butter a 2-quart casserole or large baking dish.
Pull off the outer leaves of the cabbage. Halve it and cut out the core. With a sharp knife or the shredding disc of a food processor, shred the cabbage thinly.
Bring a large pot of salted water to a boil. When it comes to a rolling boil, put in the shredded cabbage. Stir a few times until the water returns to a boil. Allow to boil for three minutes. Remove immediately and drain well.
Turn into the buttered casserole dish. Pour the cream over. Grate over the nutmeg: grind over the pepper: add a pinch of red pepper flakes and bacon bits, if using. Dot with the butter.
Bake for 15 minutes, or a little longer (if the cabbage has not absorbed most of the cream by then).