Buy small, firm turnips that feel heavy for their size. (As turnips age and grow bigger, their flavor becomes less sweet and their texture woody.) Keep them in a plastic bag in the refrigerator for up to 2 weeks. Turnips can be sautéed, mashed, boiled, pureed, roasted, or shredded raw. For a creamy mash: Boil peeled turnips until tender and mash with heavy cream, butter, nutmeg, salt, and pepper.