Prepare the chocolate cake according to the package instructions in a greased 9×13 baking pan. Bake until a toothpick inserted in the center comes out clean.
While the cake is still warm, use the end of a wooden spoon to poke holes all over the cake, approximately 1 inch apart.
In a medium bowl, whisk together the sweetened condensed milk and coconut cream until fully combined.
Evenly pour the coconut milk mixture over the warm cake, making sure it seeps into all the holes.
Allow the cake to cool completely at room temperature, about 1-2 hours. The cake will absorb the coconut milk mixture as it cools.
Once cooled, evenly sprinkle the sweetened shredded coconut over the top of the cake.
Microwave the chocolate frosting for 20-30 seconds until it becomes pourable. Pour over the coconut layer and spread evenly with a spatula.
If using, garnish with toasted coconut or almond slivers.
Refrigerate the cake for at least 1 hour before slicing to allow it to set up fully.
Serve chilled, on its own or accompanied by whipped cream or vanilla ice cream.