What did pierce egan add to the basic eggnog recipe when he created a variation of called tom and jerry?

Pierce Egan did not create the Tom and Jerry drink. It was invented in the 1800s, long before Egan's time.

The Tom and Jerry is a hot, spiked egg nog drink that typically includes:

* Hot water: This is added to the mixture of eggs, sugar, and alcohol to create a warm, comforting beverage.

* Spices: Brandy, rum, or other spirits are often used to add flavor and warmth.

* Nutmeg: This is typically grated on top as a garnish.

Pierce Egan was an English writer and journalist who was famous for his writing about sporting events and the underworld of London in the early 19th century. While he may have been familiar with the Tom and Jerry drink, there's no evidence that he created or modified the recipe.

If you're looking for more information on the Tom and Jerry, it's best to consult reputable sources such as food blogs, recipe websites, or historical records.