Fill a medium saucepan with 1 inch of water and bring it to a simmer over medium high heat.
Whisk the mango puree, sugar, lime juice, eggs, egg yolks, and salt in a nonreactive bowl that fits over the saucepan without touching the water.
Place the bowl over the saucepan of simmering water and stir constantly with a whisk and/or rubber spatula until the mango curd mixture thickens enough to coat the back of a spoon, about 10 minutes. The temperature should reach 170°
Remove the bowl from the simmering water and whisk in butter.
Strain the curd into a nonreactive bowl.
Press plastic wrap over the surface of the curd and refrigerate until chilled.
Notes
Use sweet, ripe mangos and fresh lime juice for the sweetest, most vibrant flavor.
Use a nonreactive bowl, like glass, ceramic, or stainless steel when making mango curd. Acid in the curd can react with metal, giving the curd a metallic taste. (Stainless steel is nonreactive.)
Make mango curd in a double boiler. It is highly recommended to use a double boiler when making mango curd. Double boilers heat much more gently than direct heat, which will lessen the risk of your curd breaking and your eggs scrambling.