For the mango layer: In a blender, blend the mango cubes (for pure) and orange juice until smooth.
In a small pot, add water and agar agar powder and stir to distribute the powder. Bring to a full boil, stirring frequently, making sure that all the agar agar powder has dissolved. Add sugar and mango pure and whisk until smooth. Remove from heat and taste, adding more sugar and/or lime juice as needed.
Pour the mango mixture into a mould. You can use whatever mould you like; I used a square pan, but you can also make individual ones using cups, glasses, etc. Add the 1-cm mango cubes into the mango base, distributing the cubes evenly throughout, and pushing them down to make sure they are submerged.
If desired, you can add mint leaves all throughout, pushing them into the mango base.
Note: Agar agar jelly sets at room temperature, so work quickly especially if you are making small ones. Refrigerate or leave at room temperature until the surface is set and no longer moves when you jiggle the mould.
For the coconut layer: In a small pot, combine water and agar agar powder and stir to distribute the powder. Bring to a full boil, stirring frequently, making sure that all the agar agar powder has dissolved.
Add sugar, salt, and stir until dissolved. Add coconut milk, stir to mix and remove from heat.
You can use this immediately if the mango layer has set, if the mango layer has not set, keep this mixture hot, covered, over the lowest heat setting on the stove to prevent it from setting and becoming clumpy.
Set in fridge till it sets and serve chill and enjoy.