Sift flour, sugar, and baking powder. In a bowl, cream the softened butter and sugar. Then, add the eggs and vanilla. Combine the two mixtures with the milk. Once the mixture is thick and creamy, add the hazelnut paste.
For the cream: Pour the cream into a saucepan and heat over low heat. As soon as it starts to boil, remove from heat and add chocolate and melt. The mixture should be smooth and consistent. Let it cool.
Cut the cake in half, and with a spatula, spread the inside and outside with the milk chocolate ganache. Next, arrange the Ferrero Rocher along the edges of the cake.