Pierce the sweet potatoes all over with a fork, and then bake on a shallow baking pan until soft, about 1 hour (no need to wrap in foil). Remove the potatoes to cool. Lower the oven temperature to 325 degrees F.
While the potatoes are cooling, whisk together the cream, brown sugar, bourbon, salt, and nutmeg. (You could also add cinnamon, though it may suggest pumpkin pie flavors and will over shadow the smoky bourbon flavor.)
Peel the potatoes, and then cut into 2-inch pieces and mash until very smooth. Add the mashed potatoes to the cream mixture and whisk well to thoroughly combine.
Pour the mixture into a 2-quart flameproof baking dish and bake 40 to 45 minutes. The custard will be firm but not dry looking when done.
When ready to serve, evenly sprinkle the turbinado sugar over the top. Position the blowtorch flame just above the sugar and move the flame back and forth in rows until the entire top is slightly burnt. Let stand until the sugar hardens, about 4 to 5 minutes, and then serve. (No blowtorch? Run the dish under the broiler, 4 inches from the flame, about 5 to 8 minutes.)
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Propane gas torches are highly flammable and should be kept away from heat, open flame and prolonged exposure to sunlight. They should be used only in well-ventilated areas. Follow torch manufacturer's instructions for use.
Recipe courtesy of Leslie Ann Nilsson, Sage General Store, Long Island City, NY