Preheat the oven to 180 °C (350 °F). Separate the eggs; beat the egg whites until stiff. Whisk the yolks, sugar, oil and water until pale. Stir the dry ingredients and sift them on top of the egg yolks. Using a hand mixer, mix until smooth, then fold in the whipped egg whites with a spatula. Spread the batter evenly on a 18 x 25 cm baking tin lined with parchment paper (the bottom) and bake for 25 minutes. While the sponge cake is in the oven, prepare the filling. Pour chocolate milk over the baked sponge cake immediately and set aside to cool.
Place all the ingredients for the filling in a bowl and mix until smooth. Spre- ad the filling evenly over the cooled sponge and refrigerate.
Melt the chocolate with butter in a double boiler and allow it to cool to lukewarm. Pour the glaze evenly over the coconut filling and refrigerate to allow the chocolate to set. Once cooled, cut the cake into squares and decorate as desired.