In a dutch oven with lid or heavy pot with lid, heat bacon fat (I love bacon fat!) over medium high heat.
Add chopped bacon, garlic, thyme, and crushed red pepper flakes. Cook approximately 3 minutes or until the garlic is just starting to brown.
Add cabbage and give it a stir. Then, add the bone broth and vinegar (if using) and bring to a boil.
Cover and reduce heat to a low simmer and continue to cook for 20 minutes. After 20 minutes, check the texture of the cabbage. If you wish it to be softer, cook an additional 5-10 minutes.In adjusting the texture, please note that the cabbage will continue to cook in the covered pot a bit after you turn off the heat if you are not serving it immediately.
Adjust seasonings to your liking with fine sea salt and fresh ground pepper.Serve.
If you'd like to up the umami factor, add in some shitake mushrooms 10 minutes before it's all done cooking. My mouth is watering just thinking about it!