Beat the egg yolks, sugar, cocoa, and vanilla until thick and completely blended. Stir in the milk and the Amaretto until the mixture is uniform in color. Refrigerate until very cold.
Combine the egg whites, salt, and cream of tartar in a bowl and beat until soft peaks form. With a rubber spatula, fold into the chocolate mixture.
Beat the whipping cream until soft peaks form. Add the 1 Tbs. sugar and beat until dissolved. Fold into the chocolate mixture with a rubber spatula.
Grate semi-sweet chocolate over the tops of each cup of eggnog and serve immediately.
