In a mixing bowl, combine mango puree, sugar, egg yolks, lemon juice, and cornstarch. Whisk until smooth and fully blended with no lumps.

Pour the mixture into a saucepan and place it on low heat. Begin stirring immediately using a spoon or spatula.

Continue to cook the mixture slowly while stirring constantly. Make sure to scrape the bottom and sides of the pan to prevent sticking.

After several minutes, the mixture will begin to thicken. Keep stirring until it coats the back of a spoon and holds a clear line when touched.

Remove the saucepan from heat and add the butter. Stir until the butter melts completely and the curd becomes smooth and glossy.

For a smoother texture, strain the curd through a fine sieve into a clean bowl.

Allow the curd to cool slightly at room temperature. Then cover and place it in the refrigerator.

Chill for at least 2 hours or until the curd is fully set and thick.