Maple Whipped Sweet Potatoes

6 pounds potatoes, peeled and cut into 2-inch chunks
6 cups apple cider
4 cups water
1 stick butter
2/3 cup maple syrup

Combine potatoes, cider, and water. Bring to boil and simmer until tender, about 35 minutes. Drain and shake dry.
Bring butter and maple syrup to boil. Add to potatoes and toss.
Puree in batches. Salt to taste.
Heat again until warmed through.