Take the mango puree in a saucepan and ¼ cup water (if you add sugar, you can add it now).
Cut the agar agar strands into small strips. Add these small strips to the saucepan with the mango puree.
Heat the saucepan and stir the mango mixture until the agar strands dissolve. Once the agar strands have dissolved, remove the saucepan from the heat and strain the mixture.
Pour the mango mixture into the moulds. The jelly sets as the mixture cools down.
Once it is cooled down, refrigerate the moulds for at least 2 hours. Demould before serving.
Notes
If you are adding sugar, you can add 2 tablespoons while heating the mango mixture.
The jelly stays good for a week when stored in air air-tight container in the refrigerator.
In this recipe, I have directly used agar strands while cooking, but you can soak the strands for 10 minutes to speed up the dissolving.
Though you can use canned mangoes, I would suggest using the natural ones. Choose Alphonse, Banganapalli, or Imam Pasand varieties as they are non-fibrous and juicy.
If you are using agar agar powder instead of strands, you can use 1 teaspoon.