How to Make It
In a large saucepan, cover the potatoes with water and bring to a boil. Add a generous pinch of salt and simmer over moderate heat until tender, about 20 minutes. Drain well.
In the same saucepan, melt the butter in the milk over moderate heat, then add the pumpkin puree. Press the potatoes through a ricer into a bowl and mix in the pumpkin mixture. Season with salt and pepper and serve.