Preheat oven to 350ºF (180ºC). Grease and lightly flour a 9x13 inch rectangular baking dish (pyrex glass baking dish is good), or a round spring form cake pan will also work see note below: Set aside.
Beat the 6 egg whites until soft peaks form. Add the sugar and self-raising flour, the 6 egg yolks and the ice water.
Pour batter into prepared pan, and bake in oven at 350ºF for 25-30 minutes, or until a toothpick inserted in center of cake comes out clean. (Make the Tres Leches Syrup while cake is baking). Remove cake from oven and place cake (Do NOT remove cake from baking dish) on wire cooling rack.
Note: I used a round spring form pan did not remove the cake but it took about 45 minutes to cook instead of 25-30.
To Make The Tres Leches Syrup:
In a large bowl combine the evaporated milk, sweetened condensed milk and the 2 cups whole milk. Mix well. Stir in a little rum if desired.
With a fork, toothpick or wooden skewer, poke holes all over top of cake and pour the Tres Leches syrup over the top of cake until completely absorbed.
Once cake has cooled sufficiently, refrigerate cake in baking dish for at least 3 hours or preferably overnight before frosting with whipped cream
Makes 9 - 12 servings.