Preheat oven to 350°F/177°C. Grease and line three 4-inch round pan.
In a sauce pan, mix all cream ingredients except for the butter and vanilla. Cook over low heat until thick and it coats the back of a spoon. Remove from heat, stir in the butter and vanilla. Cover with cling wrap, set aside to cool.
Prepare cake: beat together cake mix with butter until coarse and mealy. Add in egg one at a time and pour in water. Divide cake batter among prepared pans. Bake for 25-30 minutes or until baked. Place on a wire rack to cool.
Poke holes in cakes using a chopstick or a clean handle of a wooden spoon. Divide prepared cream among the cakes. Pour on top.
Refrigerate cakes to set.
Place ganache ingredients in a microwave safe bowl, heat up in 10 second intervals until chocolate melts and mixture is smooth.
Let ganache cool slightly, place inside piping bags and decorate top of cakes.