Preheat the oven at 175 degrees Celsius.
Place a baking paper in a big oven form approx. forty by thirty centimeters. Butter the paper and sprinkle some of the coconut flakes on the paper.
Mix the eggs and the sugar very fluffy and white.
Add the water, flour and the baking powder and mix it well.
Pour the batter in the oven form, and place the form in the oven for twenty minutes.
Take out the cake from the oven and let it cool down.
Mel the margarine and the white chocolate together in a casserole.
Take the casserole away from the stow and add the sugar, and the vanilla sugar. Let it cool down a few minutes and pour it evenly over the cake bottom.
Sprinkle the grated coconut on top and let the cake rest for minimum two hours.
Cut the cake in squares before serving it.