Preheat oven to 375 degrees F (190 degrees C). Place sweet potatoes on a baking sheet.
Bake sweet potatoes in the preheated oven until soft, 45 to 50 minutes. Let cool, about 5 minutes.
Peel sweet potatoes. Pass flesh through a ricer set over a bowl.
Combine heavy cream and chipotle pepper puree in a saucepan over low heat; bring to a simmer. Measure 1/4 cup of the chipotle cream into a small bowl.
Stir butter, maple syrup, and creme fraiche into the remaining chipotle cream in the saucepan. Stir enough of the mixture into the mashed sweet potatoes to reach desired consistency; season with cinnamon, nutmeg, salt, and pepper.
Grease a baking dish with butter and fill with sweet potato mixture. Drizzle remaining 1/4 cup chipotle cream on top.
Bake in the preheated oven until golden brown, about 30 minutes.