Use this recipe when making our Mango Tart. It makes enough to fill two 9-inch tart shells, three 3-by-14-inch rectangles, or up to four dozen 3-inch tartlets.
Whisk together egg yolks and whole eggs in a nonreactive saucepan. Add sugar and lime juice; whisk to combine.
Cook over low heat, stirring constantly with a wooden spoon, until the mixture thickens to almost puddinglike consistency, about 30 minutes. Remove from heat; transfer to a heat-proof bowl. Stir in butter one piece at a time, until fully incorporated. Stir in lime zest, if desired.
If not using immediately, cover surface directly with plastic wrap to keep a skin from forming, and refrigerate until ready to use.
Lime curd can be kept, refrigerated, for up to 4 days.