Remove the seeds from the squash. Brush with a thin layer of olive oil and sprinkle with 1/4 teaspoon salt. Place on a baking sheet, cut-side down. Roast until tender when pierced with a knife, 30 to 40 minutes. Let cool completely.
Scoop the flesh of the cooled squash into a food processor, discarding the skin. Add the chickpeas, tahini, chipotle, lemon juice and 3/4 teaspoon salt. Process until mostly smooth. With the machine running, drizzle in the olive oil and process until very smooth and creamy, about 1 minute. Transfer to a serving bowl and drizzle with olive oil, then sprinkle with sesame seeds and chili powder to garnish.