Preheat oven to 350 degrees F (180 degrees C).
Cream together the Butter (1/3 cup) and Granulated Sugar (2 1/4 cup) in a mixing bowl. Pour the Evaporated Milk (12 fluid ounce) into a large measuring cup, and add Water (to taste) to the cup to equal 2 cups of liquid.
Pour liquid into creamed butter mixture along with Mochiko Sweet Rice Flour (1 pound), Egg (4), Baking Powder (2 teaspoon), Vanilla Extract (1 teaspoon) and Coconut Milk (13.5 fluid ounce). Stir well.
Pour into a lightly greased 9x13 inch pan, and bake for 1 hour.
Allow it to cool, before cutting and serving. Enjoy!