Meanwhile, melt the butter in a large saucepan. Add the bacon and cook over moderately low heat until the bacon is lightly browned, about 4 minutes. Pour off all but 2 tablespoons of the fat from the pan. Add the stock and bring to a boil, then stir in the cabbage. Cover and cook over low heat, stirring a few times, until the cabbage is crisp-tender, about 5 minutes. Season with salt and white pepper, cover and keep warm.