Tip: Frozen butternut squash puree is also sometimes labeled "cooked winter squash." To make butternut squash puree from scratch, cut a butternut squash in half lengthwise. Scoop out seeds and pulp and set the halves, cut-side down, on a baking sheet lined with parchment. Bake at 350 degrees F for 50 minutes to 1 hour. When the squash is tender it will give gently when pressed through the skin. Allow the squash to cool before pureeing in a food processor. 1 large (2 1/2-pound) butternut squash makes about 2 1/2 cups puree.
To make ahead: Refrigerate sauce in an airtight container for up to 3 days or freeze for up to 3 months.
1 fat, 1 vegetable, 1/2 starch