To make butternut squash purée, halve and seed a medium butternut squash and rub 1 tablespoon (14 grams) vegetable oil onto cut sides. Bake, cut side down, on a parchment paper-lined baking sheet at 375°F (190°C) until tender, 50 minutes to 1 hour. Let cool completely, cut side up, on pan. Scoop squash into the work bowl of a food processor, and pulse until almost smooth, stopping to scrape sides of bowl. (Alternatively, mash using a potato masher.) Reserve any leftover purée for another use.