Three Key Components: 

Sherry Vinegar

Sugar

Soy Sauce 

In a medium bowl, whisk together the water and sugar to dissolve the sugar, then stir in the sherry vinegar and soy sauce.

Boil the eggs in water for 6 minutes and 50 seconds, stirring
slowly for the first 1 1/2 minutes to distribute the heat evenly.

When the eggs are done, transfer them to an ice bath.