This is adapted from the Cabbagetown Cafe cookbook. We like to make it with red cabbage for a fun color.
In a large stock pot melt the butter. Add the onion and sauté 10 minutes. Add caraway, if using, and sauté another minute.
Add the cabbage and salt. Cook over low heat, covered, until the cabbage is sweet and limp. Stir occasionally and add water if needed to prevent sticking.
Add the milk to cooked cabbage and blend with an immersion blender (or in batches in a regular blender).
Stir in cream and vinegar. Taste, add salt if needed, and heat to desired temperature.