Fill a large pan, ¾ way full with water and add the potatoes. Bring to a boil, then simmer for 20 minutes until tender.
While the potatoes boil, melt the butter in a large skillet. Add the cabbage and cook until softened. Stir in the spring onions, remove from the heat.
Drain the potatoes, add to a large bowl and mash. Stir in the cabbage and onion mix, milk and cheese into the hot potatoes. Season with salt to taste. Serve warm.
