Make the coconut cream filling:

1. Add the egg yolks, whole egg, sugar, salt and cornstarch to a medium sized mixing bowl and whisk vigorously until slightly thick and lighter in color. Set aside.
2. Combine the coconut milk, coconut cream and vanilla extract in a saucepan or saucier and stir over medium heat until scalded. You’ll know it’s ready when you see wisps of steam coming off of the surface. Be sure not to let the milk/cream boil.
3. Slowly stream the hot milk into the egg/sugar mixture while whisking quickly and constantly. Once all of the hot milk has been added, pour the tempered mixture back into the saucepan and return to medium/low heat.
4. Whisk the mixture constantly as it continues to cook. After 5-7 minutes, it should begin to thicken up. Continue whisking until the custard is the consistency of pudding.
5. Immediately remove the saucepan from the heat and whisk in the cold butter and half of the 7 oz bag of coconut flakes. Use a spatula to scrape the custard into a shallow dish and smooth the surface. Cover with a layer of plastic wrap, being sure to gently press it to the surface of the custard. This prevents a skin from forming as the it chills.
6. Allow the custard to fully chill in the fridge overnight.

Assemble and finish the tiramisu:

1. Before toasting the coconut for the topping, take the mascarpone out of the fridge. It doesn’t need to be at room temperature, but it should be just soft enough to mix with the coconut custard after about 20 minutes.
2. Add the remaining half of the 7 oz bag of sweetened shredded coconut to a small nonstick skillet.  Stir occasionally over medium heat until the coconut is toasted to a medium golden brown. Remove the skillet from the heat and transfer the coconut to a plate. Chill the plate of coconut in the fridge while you finish the filling and assemble the tiramisu.
3. Add the 16 oz of mascarpone to a large mixing bowl, followed by the chilled coconut custard. Use a spatula to fold everything together until the filling is slightly lighter in color and there are no white streaks of mascarpone remaining. Set the finished filling aside while you soak the cookies.
4. Stir the coffee and coconut rum together in a small, shallow dish so that you can easily dip the lady finger cookies. Dip each cookie in the coffee/rum mixture for a few seconds and arrange in two rows on the bottom of a 9 x 9 square baking pan. Make sure to leave about 1/4 inch between each cookie.
5. Spread half of the filling on top of the first layer of soaked lady fingers, and repeat the process with the remaining cookies and filling. Smooth the top of the cream filling to create an even surface.
6. Sprinkle half of the toasted coconut on top of the tiramisu. Using a fine mesh sieve, dust the cocoa powder on top of the coconut and then cover the cocoa with the remaining toasted flakes.
7. Cover the pan with plastic wrap and refrigerate for at least 8 hours, preferably overnight.
8. Cut into squares and serve! Use any leftovers within a week, or freeze individual portions for up to 6 months. Allow frozen tiramisu to thaw in the fridge overnight before enjoying.