First, make the syrup. In a saucepan, combine the water, vanilla, sugar, and cocoa powder. Stir well until the sugar dissolves. Add the chocolate hazelnut spread and mix thoroughly. Once it comes to a boil, transfer to another container and set aside to cool.

In a saucepan, add the butter, sugar, brandy, and vanilla sugar. Once the butter and sugar have melted, remove from heat and let cool for 15 minutes.

Pour the mixture into a stand mixer bowl or another large bowl. Add the eggs one at a time, mixing until incorporated. Gradually add the flour, mixing as you go.

Next, add all the remaining ingredients and mix until the batter is smooth. Pour into a suitable baking dish (10–12 inches in diameter) or a cake pan lined with parchment paper.

Bake at 350°F (180°C) with the fan on for about 30 minutes. Pour the cooled syrup over the cake and let it cool completely. If desired, spread more chocolate hazelnut spread, chocolate ganache, or glaze on top.