Preheat the oven to 180°C.
Mix the cake mix with the eggs and vegetable oil in a bowl until a nice, smooth batter.
Mix for 1 minute at low speed, add the butter (at room temperature).
Mix for a further 5 minutes at medium speed.
Spray in the desired baking tin with baking spray.
Divide the batter into a baking tin of your choice and make sure the tin is 3/4 full.
Bake the cake for 50 to 55 minutes in the centre of the preheated oven.
Pierce the middle of the cake (at the end of the baking time) with a thin awl, when there is no more batter, the cake is cooked.
Otherwise extend the baking time by 5 minutes.
After baking, remove the cake from the baking tin and let it cool down on a wire rack.
Put the water (25°C) with the mix and the sugar in a bowl.
Mix with a whisk for 1 minute until smooth.
Let the mixture rest at room temperature for 15 minutes.
In the meantime, beat the butter with the mixer lightly for 10 minutes at medium speed.
Add the mixture in 5 parts at the lowest mixing speed of the mixer.
It is important that the current part is always well mixed before you add the next part.
Repeat this until the whole mixture has been mixed through the whipped butter.
Now add the vanilla aroma to taste.
Beat the mixture again for 5 minutes at medium speed.
The filling is ready for use.
Cut the cake in 4 layers in half, so that there are 4 equal pieces of cake.
Press the bottom slice of cake with a thick layer of filling +/-1 cm.
Place the other layer of cake on top and press it a little.
Repeat these steps until everything is processed.
Brush the top side with the remaining filling and sprinkle generously with the desiccated coconut.
Finish the cake off with blueberries or other fruit of your choice.
Place the filled cake in the fridge for 20 minutes and then cut it into slices.