In a large bowl whip egg yolks, sugar, vanilla and salt until very light in color, fluffy, and thick. It should take around 7-10 minutes.
Add in mascarpone and whip until fluffy and the sugar is no longer grainy. Set aside.
To another large bowl, add all the hard coconut cream from the can, leaving all the liquid in the can.
Whip the coconut cream with an electric mixer, adding a tablespoon of the reserved coconut liquid from the can at a time, until a smooth, light and fluffy whip cream texture is achieved.
Fold whipped coconut cream into the egg mixture.
In a shallow dish combine coffee and rum.
Quickly dip a lady finger in the coffee mixture and transfer to an 8x8 inch dish. Be careful not to submerge the ladyfinger for too long, as they will become over soaked and will fall apart.
Continue dipping ladyfingers until you snugly fill the bottom of the dish. Cover with half of the cream mixture.
Repeat with another layer of dipped ladyfingers and the remaining cream.
Cover and refrigerate overnight.
Just before serving dust the top with cocoa powder and sprinkle with some coconut flakes if using.