For ultrafluffy potatoes, Grace Parisi presses them through a ricer. To achieve a similar texture, pass the potatoes through a food mill or a fine-mesh sieve. If you choose to mash them by hand, be gentle; otherwise, the potatoes will turn gluey. Grace offers other creative ideas for fluffy mashed potatoes like Mashed Potatoes with Parmesan Cheese and Fresh Thyme and Mashed Potatoes with Crispy Shallots. More Potato Side Dishes
Preheat the oven to 400°. In a large bowl, toss the squash with the oil and season with salt. Spread the squash on a nonstick baking sheet and roast, turning once, for about 25 minutes, until tender and lightly browned in spots. Transfer the squash to a food processor and puree until smooth.
Meanwhile, in a large pot, cover the potatoes and garlic with cold water and bring to a boil. Simmer over moderate heat until tender, about 20 minutes.
Drain the potatoes and garlic in a colander, shaking out the excess water. Add the half-and-half and butter to the pot and heat until melted. Remove from the heat. Press the potatoes and garlic through a ricer into the pot and season with salt. Stir in the butternut squash puree and cook over moderate heat until very hot. Transfer the mashed potatoes to a bowl and serve right away.
The dish can be made earlier in the day and kept at room temperature; warm over moderate heat, stirring constantly.