4 tablespoons unsalted butter, melted, plus an additional 1 tablespoon for greasing pan
3 pounds sweet potatoes, peeled and thinly sliced into 1/8-inch rounds
1 tablespoon Dutch process cocoa powder
1 tablespoon granulated sugar
3/4 teaspoon ground cinnamon
1/2 teaspoon chipotle powder
3/4 teaspoon kosher salt
1 1/2 cups roughly crushed graham cracker crumbs
1 cup half-and-half
4 cups miniature marshmallows