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Sweet Potato Soufflé

Sweet potato soufflé is baked until puffed and lightly browned, with a tender, airy texture from gently folded egg whites. Roasting the sweet potatoes first brings out their sweetness and makes a smooth base for the soufflé.
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Prep Time 20 minutes
Cook Time 1 hour 30 minutes
Resting 5 minutes
Total Time 1 hour 55 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: American
Calories: 260
Ingredients Equipment Method Notes

Ingredients
  

  • 3 cups sweet potato cooked, mashed; from about 2 1/2 pounds whole sweet potatoes
  • 5 tbsp butter unsalted, softened and divided
  • 0.33 cup light brown sugar packed
  • 0.33 cup milk whole
  • 4 eggs large, separated
  • 1 tsp vanilla extract
  • 0.5 tsp ground cinnamon
  • 0.5 tsp salt fine

Equipment

  • 1 rimmed baking sheet
  • 1 9x9-inch baking dish
  • 1 electric mixer
  • 1 instant-read thermometer

Method
 

  1. Heat the oven to 400°F.
  2. Prick the sweet potatoes all over with a fork and place them on a rimmed baking sheet.
  3. Roast for 45-60 minutes, until a knife slides easily into the centers.
  4. Let the potatoes cool until easy to handle.
  5. Halve the potatoes, scoop out the flesh, and mash until smooth; measure 3 cups.
  6. Reduce the oven to 375°F.
  7. Grease a 9x9-inch baking dish with 1 tablespoon of the butter.
  8. Melt the remaining 4 tablespoons of butter.
  9. In a large bowl, stir the sweet potato with the melted butter, brown sugar, milk, egg yolks, vanilla, cinnamon, and salt until smooth.
  10. In a clean, dry medium bowl, beat the egg whites with an electric mixer on medium-high speed for 3-5 minutes, until stiff peaks form.
  11. Fold one-third of the egg whites into the sweet potato mixture to lighten it, then gently fold in the remaining whites just until no large white streaks remain.
  12. Transfer the mixture to the prepared dish and bake for 35-45 minutes, until puffed and lightly browned and the center registers at least 160°F on an instant-read thermometer.
  13. Rest for 5 minutes, then serve promptly.

Notes

For the tallest soufflé, fold the egg whites gently and stop as soon as no large white streaks remain. Refrigerate leftovers in an airtight container for up to 4 days; freezing is not recommended because the soufflé may lose its airy texture. For a dairy-free swap, use plant-based butter and unsweetened oat milk.