Once the cake is ready, take it out and leave to cool. Start making the syrup - you'll be pouring it over the cake later. For it, put the water with the sugar and vanilla on the stove.
Once the water comes to a boil and sugar dissolves completely, add the cocoa and stir until fully dissolved as well. Then add the butter.
Once everything is thoroughly mixed, it's time to pour on the syrup. Make several holes in the cake with a toothpick and pour the hot cocoa syrup evenly. Sprinkle with coconut flakes if desired.
Leave it to sit for at least 1 hour, then cut into squares and voila, it's ready to serve.