01 - Place potatoes in a large pot and cover with cold salted water. Bring to a boil, reduce heat, and simmer for 15 to 20 minutes until tender when pierced with a fork.
02 - While potatoes cook, bring a separate pot of salted water to a boil. Add kale and cook for 3 to 4 minutes until just tender. Drain well, squeezing out excess moisture, and set aside.
03 - In a small saucepan, heat milk and butter together over low heat until butter melts completely.
04 - Drain cooked potatoes and return them to the pot. Mash thoroughly until smooth and lump-free.
05 - Stir in the warm milk and butter mixture, followed by cooked kale and most of the scallions. Mix well and season generously with salt and pepper.
06 - Transfer to a serving bowl, top with remaining scallions and a knob of butter, and serve hot.