1. Preheat your oven to 350°F or 180°C.

2. In a large mixing bowl, combine eggs, flour, cocoa powder, hot water, baking powder, and vanilla sugar. Mix these ingredients well until they form a smooth cake base.

3. In a separate bowl, cream the butter and sugar together until the mixture becomes light and fluffy. Add milk and mix until well combined.

4. Gradually add the cake base mixture to the butter mixture, mixing well after each addition to ensure a smooth consistency.

5. Divide the mixture into two equal parts and pour each part into a greased and floured cake pan.

6. Bake for 30-40 minutes, or until a toothpick inserted in the center comes out clean. Remove the cakes from the oven and let them cool completely.

7. Prepare the pear filling by whipping heavy cream until stiff peaks form. Add vanilla custard and pear-flavored fruit cream, mixing until well combined.

8. Assemble the cake by spreading the pear filling on top of one cake layer. Place the second cake layer on top and frost with marzipan.

9. Refrigerate the cake for at least 30 minutes before serving to allow the flavors to meld together.