Heat 2 inches of water or broth with about 2 Tbsp. of vinegar for every cup of water (the acid will help the egg whites coagulate quickly, which in turn helps the egg keep its shape while cooking) in a wide, shallow pan until bubbles form along the bottom and sides of the pan, but don't break away or come to the surface (or until an instant-read thermometer reads 180°). Adjust heat to maintain this temperature.


