If you plan to unmold the panna cottas spray six 6-ounce ramekins lightly with non-stick cooking spray. If you are not going to serve the panna cotta unmolded, skip this step.
Cut the mangos as close to the large seed in the middle as possible so that you have two cheeks per mango. Remove the skin and slice one of the mangos into 12 slivers, cover with plastic wrap and store in the fridge until serving. Cut the flesh from the other two mangos into chunks and puree in the blender until very smooth. Taste the puree and if it is not sweet enough for you, add a small squeeze of honey or agave nectar being careful not to overpower the flavor of the mango. Push the mango puree through a fine strainer to remove any of the fibrous strands.
Put the water in a small microwavable bowl and sprinkle the gelatin over it. Let set for 5 minutes. Microwave the gelatin for 10 seconds on high power to melt.
Put the coconut milk and coconut palm sugar in a small sauce pan over medium heat, stirring to dissolve the sugar. Heat just to the boiling point. Whisk the gelatin mixture into the coconut milk well then whisk in the mango puree. Divide the mixture evenly between the ramekins, cover with plastic wrap and refrigerate until set, about 4 or 5 hours. Can be prepared a day ahead.
Preheat oven to 350 degrees.
Spread a layer of the coconut on a sheet pan and bake for 10 - 15 minutes, stirring a few times. Watch the coconut carefully as it can go from toasted to burnt in a matter of seconds. Let cool completely.
If unmolding the panna cotta, run a sharp knife around the edges of the ramekins and place a small serving plate on top. Flip the plate and ramekin over and the panna cotta should slip out of the ramekin onto the plate. If it does not then take a hot towel and place it on the ramekin for a few seconds. Serve with reserved mango slices and toasted coconut.
If you choose not to unmold the panna cotta then simply stick a couple mango spears into the top and sprinkle on a little toasted coconut.