1. Heat oven to 400 degrees F. Place squash, cut sides down, on baking sheet.
2. Bake in 400 degrees F oven 45 minutes to 1 hour, until squash is easily pierced with fork. Cool slightly. Scoop flesh into bowl; mash until fairly smooth. Add salt and pepper. Keep warm.
3. Mix butter and syrup in saucepan. Cook, stirring, over low heat until the mixture is blended, 2 minutes.
4. Stir half of syrup mixture into squash. Transfer to serving dish. Pour rest of syrup mixture over top. Serve.