This dish can be reheated in 350 F oven for 15 minutes even after doing the brûlée. Measurements are approximate, as sweet potatoes vary so much in size.
4 1/2 cups cooked sweet potato, about 3 large, baked
1/4 cup whipping cream
1/4 cup orange juice
2 tbsp chopped chives
1 tsp grated fresh ginger
Salt and freshly ground pepper
1/2 cup grated Parmesan
2 tbsp brown sugar
Mash sweet potato in a large bowl with a fork then stir in whipping cream, juice, chives, ginger and season with salt and pepper. Alternatively use the food processor but do not turn it into mush. It should have some texture.
Scoop into a gratin dish that will go under the broiler. Combine Parmesan and brown sugar, sprinkle over gratin. Broil until top is caramelized, about 2 minutes. Garnish with chopped chives.