In a saucepan add mango puree, lemon juice, sugar and egg yolks and mix well.
Now set the saucepan over MEDIUM LOW heat.
Stir continuously with a spatula until sugar dissolves.
When sugar completely dissolves, add the butter slowly.
Keep stirring continuously and cook the mixture until it thickens and coats the back of the spatula. This will take about 6-8 minutes.
Once done, take the saucepan off the heat and pass the mixture through a fine mesh sieve. Use the spatula to press the mixture through the sieve. This will ensure that there are no lumps and the curd is smooth.
Transfer the curd to a container. Cover with a cling wrap making sure that it directly touches the top of the curd. This prevents the skin forming on the curd.
Let the curd cool and then refrigerate.
Use it after it has cooled completely.