Butternut squash has a firm rind that insulates it against cool temperatures and other environmental stressors when it's off the vine. Store a whole butternut in a 50-degree-Fahrenheit room, and it lasts 2 to 3 months, with no special care needed. Ideally, you want to keep squash whole as long as possible; it develops a complex sweetness as it matures. If you still haven't used the squash after a month or so, preserve it. Squash stores for a year in the freezer and indefinitely if canned.
Uncooked Cubed Squash
To prep uncooked butternut squash for freezing or refrigerator storage, make it easier to handle. Set it on a moist kitchen towel, and use a heavy chef's knife to slice off the thick stem and about 1/2 inch of the flesh below it. Next, slice the squash in half lengthwise, or, if it's too long to slice comfortably, slice it in half crosswise first; then slice it lengthwise. Scoop out the seeds using a spoon, and peel the skin with a vegetable peeler or paring knife.
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Slice the squash into equal-sized pieces -- 1/2- or 1-inch-cubes or slices work, just slice them as evenly as you can. To store the squash in the refrigerator, pack it in an airtight container -- it will stay fresh about 5 days. To freeze, seal the squash in heavy-duty freezer bags, pressing out the air as you do, and store in the freezer up to 6 months.
Storing Cooked Squash
You don't need to peel the squash if you plan to roast it; the skin pulls away easily, and you can slice it in pieces of the desired size after that. Heat the oven 425 degrees Fahrenheit. Cut off the stem; slice the squash lengthwise and scoop out the seeds. Roast the butternut skin-side-up until tender, about 1 hour. While the squash is still very warm, peel the skin away and discard it. Puree, slice or chop, and serve or store it.
To store, cut the squash into equal-sized pieces or puree it and pack it in an airtight container or freezer bag. You can also spoon the puree into ice-cube trays to make portioning more efficient; simply pop a few pieces out of the tray as needed. If you choose ice-cube trays, wrap each one in a freezer bag. Cooked squash stays fresh about 2 days in the refrigerator and up 1 month in the freezer.
Thawing and Cooking
You can cook raw squash straight from the freezer; simply toss it in a soup or heat it in a 350-F oven until it's hot. After you heat the squash, you can puree it and transfer it to a saucepan for use as a soup base or add herbs and spices and serve it as a stand-alone dish. You can use cooked squash straight from the freezer as well, but you must heat it to 165 F before serving.
Very dry food -- with less than 5 percent moisture -- stores almost indefinitely. It's difficult, however, to get dense vegetables like butternut squash down to 5 percent moisture unless you slice it almost paper thin; a mandolin works best for this, but at the very least, you need a sharp knife.
Heat the dehydrator to 145 F; if you're using a regular oven, heat it to the lowest setting and wedge a towel in the door to keep it open 1 to 2 inches. Peel and slice the squash in 1/8-inch-thick pieces and lay them in an even layer on the drying trays; use a sheet pan lined with parchment paper for oven drying. You can overlap the slices by about 1/4 inch. Dry the squash for 10 to 16 hours, or until it has a very tough to brittle texture.
Peel and cut the squash into 1-inch pieces and blanch them in boiling water for 2 minutes. Drain the squash in a colander and pack them into sterilized canning jars -- leave an inch of space at the top and add water or stock to barely cover. Seal the jars and process them in a pressure canner: 55 minutes for pint jars and 90 minutes for quart jars.