1. In a medium saucepan, combine sugar, 2 tablespoons water, and lemon juice. Place remaining 4 tablespoons water near stove. Bring sugar mixture to a boil over medium heat, stirring constantly; cook for 5 minutes or until mixture is dark amber in color; remove from heat.
2. Gradually and carefully add water to sugar mixture or it may spatter. Stir until sugar mixture is dissolved. In a large bowl, whisk together eggs and milk. Stir in caramel mixture. Cook over medium-low heat for about 12 minutes or until mixture coats back of spoon. Immediately strain through a cheesecloth into a 6-cup bowl. Stir in vanilla, nutmeg and salt.
3. Cover and refrigerate until chilled. Just before serving , beat together whipping cream, liqueur, if desired, and icing sugar until soft peaks form. pour chilled eggnog int 2 quart serving bowl. Fold in whipped cream with whisk.
4. Sprinkle nutmeg on top if desired.
5. TIP: For a hit of holiday spirit, add dark rum to taste. Eggnog can be prepared ahead of time. It can be kept covered, 3-4 days in the refrigerator.
6. Whisk eggnog before serving.