While the squash is roasting, place a small skillet over medium heat and wait about a minute. Add the remaining 1/2 tablespoon—that's 1 1/2 teaspoons—olive oil, and swirl to coat the pan. Toss in the butter and swirl until it melts.
Add the onion and cook, stirring often, for 10 minutes, or until the onion becomes very soft and is beginning to turn golden. (If it appears to be browning too quickly, turn the heat to medium-low.)
Add half the walnuts, and cook them with the onion, stirring frequently for five to eight minutes, or until the nuts begin to toast and give off a lovely aroma. Stir in the garlic and salt, if using, and cook 5 minutes longer. Remove the pan from the heat.
Meanwhile, lightly toast the remaining walnuts and set aside.
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After 40 minutes of undisturbed cooking, fluff the rice with a fork. Give it a taste. If it is a little too crunchy, add another 3 tablespoons water and, without fluffing or stirring it further, put the top back on and let it steam for another 10 minutes with the heat turned off. It will steam itself a little further and become more tender.
Transfer the rice to a medium-large bowl. Add the onion-walnut mixture—using a rubber spatula to scrape in all the delicious essence that might otherwise be left in the pan—and toss with a fork until well combined. Add the apple and cherries, and mix until thoroughly combined.
Turn the squash over, so their cavities face up. Divide the rice mixture among the squash, using a soup spoon to fill the cavities, packing down the filling, and then mounding the top.
Cover the filled squash loosely with a tent of foil, and return the tray to the oven for about 10 minutes— just long enough to heat through. (You can also skip this step and just serve it warm, as is. It's good either way.) Serve topped with the remaining toasted walnuts.
Please note: You can include the squash in the stuffing as well. Simply roast it as directed, peel it and cut it in chunks. Add the squash chunks to the rice mixture.
If you can't find dried cherries, substitute dried cranberries.
Nutritional Information (per serving): 290 calories; 10 g fat; 23 g carbohydrate; 6 g fiber; 5.5 g protein; 10 mg sodium
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