If using clear jel, sprinkle it over the mango and process
Once mango is pureed, place in a saucepan over low-medium heat.
If using cornstarch, dissolve in water and whisk into mango once the mango is heated.
Regardless of whether you used cornstarch or clear jel, continue to whisk your mango until it is thick and to prevent sticking/burning (1-2 minutes for the cook type clear gel)
Once thick, add the lime juice and remove from the heat.
Let cool completely.
I put mine in the refrigerator overnight, but I can't promise that the mixture with the cornstarch would remain nice and thick if refrigerated overnight.