Lime Curd Beat butter and sugar in a large bowl using an electric mixer. Slowly add the eggs and yolks one at a time, mixing well after each addition. Pour in lime juice and mix again. Expect the mixture to look curdled, this is normal.
Cook the mixture over medium heat in a medium-size saucepan until it looks smooth (no longer curdled.) Increase the heat slightly and cook, whisking constantly, until the mixture thickens. Clip a thermometer to the side of the pan and cook until the mixture reaches 170 degrees.
Remove the curd from the heat. Transfer the curd to a bowl and press plastic wrap on the surface of the lime curd to keep a skin from forming. Chill the curd in the refrigerator. The curd will thicken further as it cools. Covered tightly, it will keep in the refrigerator for a week and in the freezer for 2 months.