For the birthday cake hydrangea beat eggs, baking sugar and vanilla sugar until foamy. Then stir in water and oil alternately. Sift flour with cocoa and baking powder and stir in. Pour the mixture into a greased cake tin (diameter 26 cm) and bake at 180 °C for approx. 1 hour.
For the coffee buttercream, bring whipping cream to a boil and add coarsely chopped coffee chocolate, wait about 1 minute, mix well and let cool. Beat butter for about 10 minutes until fluffy and stir in the cooled coffee chocolate mixture.
Cut cake in half twice and fill with coffee buttercream. Prick with apricot jam.
Knead white fondant until soft, roll out and place over cake.
Finally, decorate birthday cake hydrangea as desired with pearl ribbon and homemade hydrangea flowers and ivy leaves made of fondant.