Prepare butter cake according to package directions.
While cake is baking, drain crushed pineapple into a bowl (saving the juice).
In a separate bowl, whisk together cream of coconut, sweetened condensed milk and pineapple juice.
When you open the can of cream of coconut, you will probably see that some of the coconut oil and cream have separated so it's really important that you whisk this mixture so you get it combined and get most of the lumps out.
Once combined, mixture will be thin.
Once cake is done, take it out of the oven.
While cake is still warm, begin poking holes in the top using a fork or other similar size utensil.
Then pour cream of coconut mixture evenly over cake.
It will look pretty saturated. But don't worry the cake is going to soak it all up.
Once cake is completely cooled, top it with crushed pineapple.
Then spread Cool Whip on top.
Then sprinkle shredded coconut on top of the Cool Whip. (You can toast your shredded coconut if you like)
Slice and serve.
This cake needs to be kept refrigerated. Make sure you cover it with some plastic wrap or a lid.