Wash the shells of the eggs gently with warm soap and water to remove bacteria and separate yolks and whites.
Whisk egg yolks, brown sugar and salt until thickened and pale brown in color, 2 to 3 minutes. Whisk in the cream and milk, then the alcohol (if using) and vanilla.
Whip egg whites in a large clean bowl using an electric mixer on medium speed until soft peaks form, about 2 minutes. Gradually add sugar and continue whipping until firm, glossy peaks form, about 1 minute longer.
Fold in egg whites with a rubber spatula transfer to a punch bowl or ladle portions into cups. Sprinkle with freshly grated nutmeg and serve.