- 3 pounds large sweet potatoes
- 6 tablespoons unsalted butter, softened
- 1/2 cup heavy cream
- 1/2 cup shredded Gruyère cheese
- 2 tablespoons light brown sugar
- 1 teaspoon chopped thyme
- Salt and freshly ground pepper
- 3 large eggs
Preheat the oven to 350°. Bake the sweet potatoes for 1 1/2 hours, or until tender. Raise the oven temperature to 425°.
Peel the sweet potatoes as soon as they are cool enough to handle; transfer to a bowl. Using a handheld electric mixer, beat the sweet potatoes with the butter until smooth. Beat in the cream, Gruyère, brown sugar and thyme; season with salt and pepper. Beat in the eggs one at a time, beating well after each addition.
Transfer the sweet potato puree to a buttered 8-by-11-inch baking dish and bake for 15 minutes. Reduce the oven temperature to 400° and bake for 30 minutes longer, or until the sweet potatoes are lightly puffed and browned. Let the sweet potato soufflé rest for 10 minutes before serving.