3 large eggs
¾ cups sugar
¼ cup freshly squeezed key lime juice*
4 tbsp. (2 oz.) unsalted butter, at room temperature, cut into pieces
In a non-reactive saucepan, combine the eggs and sugar. Whisk together until well blended. Whisk in the key lime juice. Place the pan over medium-low heat. Cook, stirring or whisking constantly, until the mixture is warmed through. Be careful not to heat the mixture too quickly to avoid curdling the eggs. Whisk in the butter a little bit at a time, stirring in each addition until completely incorporated before adding more. Continue to cook, scraping the bottom of the pan, until the mixture thickens and a spoon or spatula leaves a path when drawn through it (no higher than 175˚ F on an instant-read thermometer.) Immediately remove the pan from the heat and pass the mixture through a fine mesh strainer. Transfer to an airtight container and refrigerate. (This keeps up to 2 weeks in the refrigerator.)
*This can certainly be made with regular old limes if you can’t find key limes, as well as other types of citrus – lemon, orange, etc.