Sweet Potato Souffles

Preheat an oven to 375°F (190°C).

Pierce the potatoes two or three times with a fork and place on a baking sheet. Bake until easily pierced with a knife, about 40 minutes. Remove from the oven and let cool. Cut in half and scrape out the pulp into a bowl. Using a potato masher, mash to form a smooth puree; you should have 2 1/2 cups. Leave the oven temperature set at 375°F.

Butter four 2-cup (500-ml) cocottes and dust the bottoms and sides with 1/4 cup (1 oz./30 g) of the Parmesan.

In a large saucepan over medium heat, melt the butter. Add the onion and sauté, stirring occasionally, until soft, about 10 minutes. Meanwhile, in a small saucepan over medium heat, warm the milk until small bubbles appear along the edges of the pan; remove from the heat. Add the flour to the onion and cook, stirring constantly, for 3 minutes. (Do not brown.) Whisk in the milk all at once and simmer, continuing to whisk, until thickened, 2 to 3 minutes. Remove from the heat and stir in the nutmeg, allspice and ginger. Add the egg yolks one at a time, beating well after each addition. Add the sweet potato puree and the Gruyère cheese and stir until well blended. Season with salt and pepper.

In a bowl, using an electric mixer, beat the egg whites on high speed just until stiff peaks form. Using a rubber spatula, fold one-fourth of the egg whites into the sweet potato mixture to lighten it. Then gently fold in the remaining whites just until no white streaks remain. Divide evenly among the prepared soufflé dishes. Sprinkle with the remaining 1/4 cup (1 oz./30 g) Parmesan.

Bake until puffed and golden, 20 to 25 minutes. Serve immediately. Serves 8.

Adapted from Williams-Sonoma Seasonal Celebration Series, Autumn, by Joanne Weir (Time-Life Books, 1997)