Purée of Yukon Gold Potatoes with Parmesan

Put the quartered potatoes in a large saucepan with enough cold water to cover. Partially cover the pot and bring to a boil. Uncover, add the salt, and reduce the heat so the water boils gently. Cook until the potatoes are tender when pierced with a fork, 10 to 12 minutes. Meanwhile, heat the milk and cream on the stovetop or in a microwave until hot but not boiling. Drain the potatoes and return to the warm pan over low heat for 1 minute, shaking the pan to dry the potatoes thoroughly. Use a potato masher, a ricer, or a food mill to mash the potatoes. Blend the butter and Parmigiano into the potatoes. Gradually add the milk mixture until the purée is as soft and moist as you like. Add salt and pepper to taste. Serve immediately or keep warm in the top of a double boiler (or in a heatproof bowl set over a pan of simmering water).