01 - Place the potatoes in a large pot and cover with cold, salted water. Bring to a boil, then simmer for 15–20 minutes until fork-tender.
02 - While the potatoes cook, melt 2 tbsp of the butter in a large skillet over medium heat. Add the kale and cook for 4–5 minutes, stirring, until wilted and tender. Add the spring onions and sauté for another 2 minutes. Set aside.
03 - Drain the potatoes well and return to the pot. Allow the steam to escape for 1–2 minutes.
04 - Mash the potatoes thoroughly. Add the remaining butter and the milk, mixing until smooth and creamy.
05 - Fold in the sautéed kale and spring onions. Season generously with salt and pepper.
06 - Transfer to a serving dish, make a well in the center, and add a knob of butter to melt. Serve warm.