Instructions:

Preheat your oven to 375°F (190°C). Grease a 1.5-quart soufflé dish with butter and lightly dust it with flour, shaking out any excess. This will help the soufflé climb the sides of the dish as it bakes.

In a medium saucepan, melt the 2 tablespoons of butter over medium heat. Once melted, add the flour and whisk continuously for about 1-2 minutes until it forms a paste (roux). Gradually add the milk, whisking constantly to avoid lumps. Cook until the mixture thickens and bubbles, about 5 minutes.

Remove the saucepan from the heat and stir in the grated Gruyère cheese, salt, nutmeg, black pepper, and cayenne pepper (if using). Allow the mixture to cool slightly before adding the egg yolks, one at a time, mixing well after each addition.

In a separate clean bowl, beat the egg whites with an electric mixer on medium-high speed until stiff peaks form. This process is vital for achieving the soufflé's light texture.

Gently fold one-third of the beaten egg whites into the cheese mixture to lighten it. Then, carefully fold in the remaining egg whites, being cautious not to deflate them. The batter should be light and airy.

Pour the soufflé mixture into the prepared dish and smooth the top. Place it in the preheated oven and bake for 25-30 minutes, or until the soufflé is puffed and golden brown on top. Avoid opening the oven door during baking, as this can cause the soufflé to collapse.

Once baked, remove the soufflé from the oven and serve immediately, as it will begin to deflate shortly after being taken out.