Pick a squash that is rock solid and heavy for its size. Its skin should be matte; a shiny finish is a sign that the squash wasn’t ripe when it was picked. Store butternut squash in a cool, dry place (not in the refrigerator) up to a month. If you don’t use the whole squash, wrap a cut uncooked piece in plastic and refrigerate it up to two days. To prepare squash for cooking, peel with a y-shaped peeler, halve lengthwise with a serrated knife, scoop out the seeds, and cut as desired. Roasting butternut squash renders it sweet and tender. It can also be sautéed or boiled and mashed.