preheat the oven to 180°. grease the base of an 8 1/2 inch spring release cake pan and wrap a piece of folded, greased baking parchment around the outside to increase the height of the pan by about a third.

seperate the eggs. beat egg yolks with half of the sugar and the vanilla extract until foamy. sift the flour and cornstarch over the mixture and fold in.

whisk the egg whites until they form soft peaks.then trickle in the remaining sugar and continue whisking until they form stiff peaks. fold the whisked egg whites into the egg yolk mixture.turn the batter into the prepared cake pan and smooth the top.

bake in the oven for 25-30 minutes until a wooden cocktail stick inserted in the middle comes out clean. leave to cool slightly, then carefully turn onto a wire rack and let the cake rest for atleast 2 hours.

for frosting, put cornstarch, cocoa powder and sugar in a bowl and mix together with a little cold milk until smooth. put the remaining milk in a saucepan, bring to a boil and stir in the cornstarch mixture. return to a boil briefly, then remove from heat. break in the gianduja and stir until the chocolate is melted. finally stir in the butter one tbsp at a time and allow to cool.

split the cake twice horizontally. spread half of the frosting smoothly over the two layers of cake. reassemble the cake with thr unfrosted layer on top. spread the top and sides of the cake with the remaining cream. chill and serve