FO' MAKE CAKE:
Prepare cake mix according to package directions using 2/3 cup of the coconut milk, the water, and the egg whites. Cool cake, remove from pan and split carefully into 3 layers. Reserve top layer; spread haupia filling on the remaining layers. Chill layers until filling is set.
While layers are chilling: soften gelatin in remaining 1/3 cup coconut milk; dissolve over hot water. Cool. Whip cream; fold in gelatin mixture, sugar and extract. Stack chilled cake layers; frost with whipped cream mixture. Sprinkle cake with coconut.
FO' MAKE HAUPIA FILLING:
In a sauce pan heat coconut milk (do not boil). Mix sugar, salt, and cornstarch with water; stir into hot coconut milk. Cook, stirring constantly, until mixture thickens (cook over low heat to avoid curdling). Stir in vanilla and cool.
NOTE: It is best to chill the haupia until it is somewhat thick, but still spreadable; otherwise it kind of goops up when you try to spread it on the layers. Chill the frosting, too, before you spread it.