In a large Dutch oven, saute bacon until crispy. Remove bacon bits to a paper-towel lined bowl. Leave the drippings in the pot. (If not using bacon, simply melt the butter in the pot.).
Add onion to hot fat with a pinch of salt. Saute slowly until limp and translucent, 10 minutes.
Add cabbage and toss. Season with more salt. Saute until cabbage begins to wilt, 5 minutes.
Add cream. Reduce heat to low, cover and braise, stirring occasionally, until cabbage is very soft and flavors are blended, 25-45 minutes (depending on the size of your cabbage). Finish with grated nutmeg, if desired.