Place the shredded cabbage, red onion and apples into the slow cooker.
Add the vinegar, brown sugar, mixed spice, salt and black pepper. Toss well to combine.
Add the cinnamon stick and dot the butter over the top.
Cover and cook on high for 4 hours or low for 6 - 8 hours, until the cabbage is completely tender and glossy.
Remove the cinnamon stick and stir well before serving.
