Whisk egg yolks on high speed for five minutes until thick and creamy.
Beat butter and sugar together, then mix in lemon zest, vanilla, yolks, flour, and cornflour.
Whisk egg whites to soft peaks and fold gently into the batter.
Preheat the grill to high.
Grease a 20cm round springform tin and line with parchment paper.
Spread a thin layer of batter in the tin and grill 10cm below heat for two minutes.
Repeat layering and grilling for 20 layers, alternating between light and dark golden-brown.
Cool in the tin for five minutes before transferring to a wire rack.
Brush the cooled cake with sieved, melted apricot jam.
Boil butter, syrup, rum, and vanilla, then stir in chocolate to create a glaze.
Pour the chocolate glaze evenly over the cake.
Mix icing sugar, rum, vanilla, and milk into a smooth glaze and drizzle over the chocolate.