5 pounds sweet potatoes (about 8 large),scrubbed
1 1/2 to 2 canned chipotle chiles in adobo sauce*, minced and mashed to a paste (about 1 tablespoon)
3 tablespoons unsalted butter, cut into pieces and softened
1 teaspoon maple sugar
Freshly ground black pepper
*available at some supermarkets and specialty foods shops. Maple sugar is about twice as sweet as regular sugar. When making maple syrup, boil down the maple sap 20 to 50 percent, until it is thick. If you keep boiling down the syrup until the liquid is gone, then you have maple sugar.