Beat eggs, add bourbon and rum slowly with stirring to prevent precipitation of egg proteins. Beat heavy cream separately until it peaks and add to the egg/bourbon/rum mix.
Add the light cream with stirring. Add the sugar, then add nutmeg to taste.
Leave standing overnight with lid slightly ajar in refrigerator, then seal with plastic or lid completely. After three weeks, strain to remove any egg solids, then serve.
NOTE: If you are looking for an eggnog that has less of a kick
(but why would you?) Cook’s Illustrated suggests following the recipe below and adding the cream right before serving:
Cook’s Illustrated Eggnog December 2013
1 dozen eggs
1 1/2 cups bourbon
1/2 cup cognac
1/2 cup dark rum
1 1/2 cup sugar
Refrigerate above in airtight container for three weeks, then strain. This mixture contains 18% alcohol.
Add to above mixture:
6 cups whole milk
1/2 cup cream
The mixture now contains 8% alcohol, according to Cook’s Illustrated. Their rule of thumb is to that for every egg, use 1 1/2 ounces of 80 proof liquor and leave out the dairy until serving time.