Preheat the oven to 180°C (fan 160°C). Grease and line a 20 cm round cake tin. In a large bowl, whisk the eggs and sugar over a pan of simmering water until warm and frothy. Remove from heat and beat until pale and thick.

Gently fold in the sifted flour and salt using a spatula, taking care not to deflate the mixture. Drizzle in the melted butter and vanilla, folding just until combined. Pour into the tin and bake for 25 to 30 minutes until golden and springy.

Let the cake cool in the tin for 10 minutes, then turn out onto a wire rack. Once fully cooled, slice horizontally into two even layers using a serrated knife. Set aside while you prepare the custard.

In a saucepan, heat the milk until just steaming. In a separate bowl, whisk the egg yolks, sugar, cornflour, and salt until smooth. Slowly pour the hot milk into the yolk mixture, whisking constantly to temper the eggs.

Return the mixture to the saucepan and cook over medium heat, stirring constantly until thickened and bubbling. Remove from heat and stir in the vanilla. Transfer to a bowl, cover with cling film touching the surface, and chill until set.

Place the bottom cake layer on a serving plate. Spread the chilled custard evenly over the surface, leaving a slight border. Gently place the second cake layer on top, pressing lightly to secure.

In a small saucepan, heat the cream until just simmering. Remove from heat and add the chopped chocolate and butter. Let sit for a minute, then stir until smooth and glossy. Allow to cool slightly for easier spreading.

Pour the glaze over the top of the cake, letting it gently run to the edges. Use a spatula to guide it if needed. Avoid glazing the sides for a traditional finish. Let the glaze set at room temperature.

Refrigerate the assembled cake for at least 1 hour to allow the custard to firm and the glaze to set. This also makes slicing cleaner and more precise.

Slice with a sharp knife dipped in hot water for neat portions. Serve chilled or at room temperature. A dusting of icing sugar or a few fresh berries on the side adds a touch of elegance.