Around the holidays, cooked, peeled chestnuts show up in jars in specialty shops and some grocery stores, so it’s a good time to stock up. Low in fat, they add a nutty sweetness to this squash dish. Rice vinegar was used here because of its clean, neutral flavor, but you could also use cider or red wine vinegar.
1. Preheat oven to 450°F. Combine squash, onion, and 2 Tbs. olive oil in large bowl, and toss to coat. Season vegetables with salt and pepper, if desired, and scatter evenly on baking sheet. Roast vegetables 20 minutes, turning 2 or 3 times with spatula.
2. Meanwhile, whisk together remaining 1 Tbs. oil, maple syrup, rice vinegar, and red pepper flakes in small bowl. Season with salt and pepper, if desired.
3. Place chestnuts in medium bowl, and add 1 Tbs. maple syrup mixture. Toss to coat.
4. Increase oven temperature to 500°F. Scatter chestnuts among squash and onion wedges. Roast vegetables 10 minutes more, or until tender. Transfer vegetable-nut mixture to large serving bowl, drizzle with remaining maple syrup mixture, add chopped chives, and toss to mix.