Prepare the white cake according to the package directions for a 9×13 inch pan. Bake and let it cool slightly on a wire rack.
While the cake is still warm, use the handle of a wooden spoon or a fork to poke holes all over the top of the cake, about 1 inch apart.
In a medium bowl, whisk together the sweetened condensed milk, full-fat coconut milk, cream of coconut, and coconut extract until fully combined. This is your sweet coconut milk mixture.
Slowly pour the coconut milk mixture evenly over the entire surface of the warm cake, allowing the liquid to soak into the holes.
Cover the cake and refrigerate for at least 4 hours, or preferably overnight, to allow the cake to fully absorb the moisture.
Before serving, spread the thawed whipped topping evenly over the top of the chilled cake.
Sprinkle the toasted flaked coconut over the whipped topping. Slice and serve this creamy coconut dessert.
Notes
To toast the flaked coconut, spread it in a single layer on a baking sheet and bake at 350°F (175°C) for 5 to 10 minutes, watching closely to prevent burning.
For a tropical coconut dessert variation, you can fold 1 cup of crushed pineapple (drained well) into the whipped topping before spreading it on the cake.
This recipe is a great potluck dessert because it travels well when kept chilled.