Drill or punch a small hole into the bottom of each coconut. (Do this one at a time) Allow the coconut water to drain into a large bowl and set a side.
With a hammer, gently tap the shell until it cracks. Do this to all the coconuts.
Place the coconuts on a roasting pan and put into an oven that has been pre-heated to 350°F degrees. Leave in oven for approximately 15 minutes.
Once you have removed the coconuts from the oven, use a pair of pot holder mittens to hold and hit the shells with a hammer once again until it breaks completely into pieces. This would be a good time to have someone else helping you. With a small paring knife you should be able to remove the coconut meat from the shell without to much trouble. That was the reason I had you place the coconuts in the oven.
Peel off the brown skin remember you want only the white coconut meat. Once you have finished peeling all of the coconut rinse under cold water, pat dry and set aside.
Now comes the fun part. If you are using a blender set it to grate add a few pieces of coconut at a time and run the machine once you see that you have a shredded texture remove from the blender and place in a large clean bowl or pot. Continue until you have grated all of the coconut.
If you are using a food processor try using the grating disk, if not then use the metal blade. And continue as explained above.
For those of you that are lucky enough to have a juicer your almost finished. Place a few pieces of coconut in the machine at a time and just catch the milk as it flows.
For the blender and food processor group, place about a handful of shredded coconut in a piece of clean linen or cheese cloth and squeeze out the milk into a clean bowl or large pot. Once you have done this put the shredded coconut you have just squeezed in a separate bowl, and continue this process until you have used all of the coconut.
If you were lucky enough to get the most milk out of your coconuts you should have about 4 cups of milk, if not don't worry we will fix that right now.
Do you remember the coconut water you saved, the first thing I want you to do is taste it if it is sweet to the taste we will use it if not, we'll go to plan "B".
Check to see how much liquid you need to make up the four cups needed for the recipe.
If the coconut water is good pour it into bowl that has the shredded coconut you used and mix it well. Now place it back into the cloth and squeeze it for all it's worth this should make up the difference. If you find that the coconut water is to bitter to use, boil a little more water than you need to make up the difference. Allow to cool a little, but while still hot pour over the shredded coconut and follow the same procedure as above.
Pour cornstarch in a bowl and slowly stir in one cup of coconut milk making sure to blend in all of the cornstarch and set aside. Pour the remaining 3 cups of milk in a pot place on the stove and bring up to heat slowly . Add Sugar, salt, and vanilla. Stir in the milk and cornstarch mixture. You must be careful not to create any lumps stir continuously so as to get a nice creamy blend. When you see that is starting to get thick lower the heat and allow to simmer at a slow boil for about another 2 to 3 minutes.
Pour mixture into a chilled mold or bowl, allow to cool for a while and then place in the refrigerator until it has set. When you are ready to serve it place a platter over the open end and flip over so that it slides on to the platter. You can garnish with sliced mango, strawberries or have it just as it is.