Start with the Custard: In a medium bowl, whisk the egg yolks and caster sugar together until pale and creamy, about 2 minutes. Whisk in the cornflour until no lumps remain. Set aside.

Heat the Milk: Pour the milk and double cream into a medium saucepan. If using a vanilla pod, scrape the seeds into the milk and add the pod. If using paste, add it now. Heat over a medium heat until it's just simmering (you'll see small bubbles around the edge). Do not let it boil.

Temper the Eggs: This is a crucial step for smooth custard. Slowly pour about half of the hot milk mixture into the egg yolk bowl, whisking constantly. This gently raises the temperature of the eggs without scrambling them. I used to struggle with lumpy custard until I discovered this tempering technique. It guarantees a silky-smooth result every time.

Cook the Custard: Pour the tempered egg mixture back into the saucepan with the remaining milk. Cook over a medium-low heat, whisking constantly, for about 5-7 minutes, until the custard thickens significantly. It should be thick enough to coat the back of a spoon. Remove from the heat and stir in the cold butter until it has melted completely.

Chill the Custard: Strain the custard through a fine-mesh sieve into a clean bowl to remove any potential lumps (and the vanilla pod, if used). Press a piece of cling film directly onto the surface of the custard to prevent a skin from forming. Refrigerate for at least 2-3 hours, or until completely cold and set.

Make the Vanilla Cake: Preheat your oven to 180°C (160°C fan) and grease and line two 20cm (8-inch) round cake tins. In a bowl, whisk together the plain flour, baking powder, and salt. In a separate large bowl, use an electric mixer to beat the softened butter and caster sugar until light and fluffy, about 3-4 minutes.

Combine Cake Ingredients: Beat the eggs into the butter mixture one at a time, followed by the vanilla extract. Add the flour mixture in three additions, alternating with the milk in two additions, beginning and ending with the flour. Mix on a low speed until just combined – do not overmix.

Bake the Cakes: Divide the batter evenly between the prepared tins and smooth the tops. Bake for 30-35 minutes, or until a skewer inserted into the centre comes out clean. Let the cakes cool in their tins for 10 minutes before turning them out onto a wire rack to cool completely.

Assemble the Pie: Once the cakes are completely cool, place one layer on your serving plate. Give the chilled custard a good whisk to loosen it up, then spread it evenly over the bottom cake layer, leaving a small border around the edge. Carefully place the second cake layer on top. Chill the assembled cake for 30 minutes while you make the glaze.

Make the Chocolate Glaze: Place the finely chopped chocolate in a heatproof bowl. Heat the double cream and golden syrup in a small saucepan until it just begins to simmer. Pour the hot cream over the chocolate and let it sit for 5 minutes without stirring. Then, whisk gently from the centre outwards until you have a smooth, glossy glaze.

Glaze and Chill: Let the glaze cool for about 10-15 minutes, until it's slightly thickened but still pourable. Pour it over the top of the chilled cake, using a spatula to gently spread it to the edges, allowing some to drip down the sides for a classic look. Return the cake to the fridge for at least 1 hour for the glaze to set before serving.