Add the butter, potato and onion iton a large saucepan and stir until well coated. Season with salt and pepper. Cover and sweat on a medium heat for 6-10 minutes. Add the stock and bring to a boil, reduce heat and simmer until vegetables are soft.

To make the buttered cabbage, wash and remove outer leaves, then divide the whole cabbage into 4 sections. Cut out the stalks and then cut into fine shreds across the grain.

Put 3 tbsp of water into a large saucepan and bring to a boil. Add the cabbage and toss constantly over a high heat, for about 3-5 minutes. Cover for another 2 minutes and then toss again. Add more salt and pepper if needed then add the remaining 1 1/2 oz of butter.

Remove from heat.

Puree the potato and onion mixture in a blender and return to the pan. Add the cabbage to the soup. Thin the soup with the milk to the consistency you desire.