Preheat oven to 400 degrees. Place squash on a rimmed baking sheet. Drizzle with oil, season with salt and pepper, and toss. Spread squash in a single layer. Place garlic on a piece of parchment-lined foil. Drizzle with oil, and wrap loosely. Place on baking sheet with squash. Bake until squash is soft and golden brown, about 50 minutes. Let cool slightly.
Meanwhile, melt 4 tablespoons butter in a skillet over medium heat. Add scallions, and cook, stirring occasionally, until softened, about 4 minutes.
Scoop flesh from squash, and transfer to a food processor. Squeeze garlic from skins, and add to squash. Add scallions and chipotles, and pulse until smooth. Add remaining 6 tablespoons butter, the sour cream, cream cheese, Parmesan, and lemon juice, and pulse until just combined but not smooth. Season with salt and pepper.
Pour into a hollowed-out squash or a serving bowl. Refrigerate for 1 hour. Sprinkle with paprika, and garnish with pepitas. Serve with breadsticks.