Butter (for the dish)
3 1/2- to 4-pound butternut squash, halved and seeded
1 teaspoon olive oil
Salt and pepper, to taste
1/2 teaspoon nutmeg, or to taste
1 cup grated Gruyere cheese
2 eggs, separated
1 extra egg white
Pinch of salt
Squeeze lemon juice
1. Set the oven at 375 degrees. Generously butter a 4-cup souffle dish.
2. Brush the squash all over with oil, then sprinkle it with salt and pepper. Place it cut-side down in a baking dish and cook it for 30 minutes or until it is tender.
3. Spoon 2 1/2 cups of squash flesh into a skillet. Add the nutmeg and cook over medium-low heat for 10 to 15 minutes or just until the moisture evaporates. Remove the pan from heat and stir in the Gruyere.
4. In the bowl of a mixer, combine the puree with the yolks.
5. In a separate bowl, beat the 3 whites until they hold medium peaks. Add the salt and lemon juice and beat until stiff.
5. Stir half of the whites into the squash puree, then gently fold in the remaining whites.
6. Spoon the mixture into the prepared dish and set the dish in a baking pan. Add enough water to come halfway up the sides of the dish and bake for 20 to 25 minutes, until the top has puffed up and browned. Serve at once.
Adapted from Robert Harris