4 cups heavy whipping cream
2 vanilla beans, split in half lengthwise
2 (3-inch) cinnamon sticks
1/2 cup sugar
12 egg yolks
1/3 cup canned chestnut purée
8 tablespoons turbinado sugar
Preheat oven to 300°. In a small saucepan over medium heat, combine cream, vanilla bean, cinnamon sticks, and sugar. Bring to a simmer, remove from heat, and cover. Let stand 15 minutes, then remove vanilla bean and cinnamon sticks.
In the container of a blender, add egg yolks. Turn to low speed, and slowly pour in cream mixture. Add chestnut purée and salt; blend until combined.
Divide chestnut mixture evenly between 8 (6-ounce) ramekins. Place ramekins in a baking dish, and fill dish with water until about halfway up the ramekins.
Bake until custard is set, about 45 minutes. Carefully remove from oven, let cool to room temperature in water; remove from water and refrigerate at least 1 hour.
Position oven rack 6 inches from broiler. Preheat oven to broil. Top each custard evenly with 1 tablespoon sugar. Broil in groups of 4 until sugar is melted and lightly browned, about 5 minutes.