3 Tbsp unsalted butter, plus extra for greasing the dish
1/4 cup finely grated parmesan (I use parmigiano-reggiano) cheese, plus extra for sprinkling
3 Tbsp all-purpose flour
1 cup scalded milk
Kosher salt and freshly ground black pepper
Pinch of cayenne pepper
Pinch of nutmeg
4 extra-large egg yolks, at room temperature
3 oz blue cheese, chopped (I use Great Hill Blue)
5 extra-large egg whites, at room temperature
1/8 tsp cream of tartar
Preheat the oven to 400°F. Butter the inside of an 8-cup souffle dish (7-1/2 inches x 3-1/4 inches deep) and sprinkle evenly with parnesab. Melt the butter in a small saucepan over low heat. With a wooden spoon, stir in the flour and cook, stirring constantly, for 2 minutes. Off the heat, whisk in the hot milk, 1/2 tsp salt, 1/4 tsp black pepper, the cayenne and nutmeg. Cook over low heat, whisking constantly, for 1 minute, until smooth and thick.
Off the heat, while still hot, whisk in the egg yolks, one at a time. Stir in the blue cheese and 1/4 cup of parmesan, and transfer to a large mixing bowl.
Put the egg whites, cream of tartar, and a pinch of salt in the bowl of a Kitchenaid-type stand mixer fitted with the whisk attachment. Beat on low speed for 1 minute, onmedium speed for 1 minute, then finally on high speed until they form firm, glossy peaks.
Whisk one quarter of the egg whites into the cheese sauce to lighten, and then fold in the rest. Pour into the souffle dish, then smooth the top. Draw a large circle on top with the spatula to help the souffle rise evenly, and place in the middle of the oven. Turn the temperature down to 375°F. Bake for 30-35 minutes (don't peek!) until puffed and brown. Serve immediately.