Instructions

Making the Cake (45 minutes + 30 minutes baking + approx. 1 hour cooling)

1. Preheat the oven to 350 F, making sure the rack is in the middle of the oven.  Lightly butter a 9-inch round springform cake pan and line with parchment paper.
2. Stir together the flour, baking powder, and salt until well blended.  Set aside.
3. Place the milk and butter in a small saucepan and set over low heat, stirring occasionally.  Once the mixture begins to simmer, turn it to very low heat until ready to use.
4. Crack the eggs into the bowl of a stand mixer and add the caster sugar.  Whisk on medium low speed for a couple minutes, then turn the speed to high and whisk until the mixture has at least doubled in volume and is quite pale.  When the whisk is lifted, a ribbon of batter should fall from it and hold its shape for a few seconds before sinking into the mixture.
5. Gently fold in the dry ingredients, then trickle in the hot milk mixture and the vanilla extract with the mixer on a low speed until well blended.  Be careful not to overmix; you want to keep as much air in the mixture as possible, but still have an evenly mixed batter.
6. Hold the bowl a little above the prepared pan and gently ease the batter into the pan, making sure the batter is level.
7. Bake the cake at 350 F for 30-40 minutes, until the cake is golden brown, is shrinking away slightly from the sides of the pan, and springs back quickly when you lightly press on the center of the cake.  Don’t open the oven door while it’s baking, or the cake may sink.
8. Let the cake cool for 10 minutes in the pan, then take it out and place it right side up on a wire rack to cool completely.

Making the Crème Pâtissière (20 minutes + cooling)

1. While the cake is cooling, make the crème pâtissière.  Pour the milk into a heavy-based medium saucepan and set over medium heat, stirring occasionally, until the milk is just barely simmering.
2. While the milk is heating, whisk the egg yolks and caster sugar together with a handheld electric mixer until the mixture is quite pale and thick.  Beat in the cornstarch and flour until well blended and very thick.
3. Once the milk is simmering, remove it from the heat and let it cool for 30 seconds.  Turn on the mixer on low and gradually trickle in the hot milk.  Whisk until well blended, then pour the mix back into the saucepan.
4. Whisk the custard constantly over medium heat until it boils and thickens.  Immediately remove it from the heat, stir in the vanilla, and pour into a medium bowl.  Cover the bowl with plastic wrap, making sure to press the wrap right onto the surface of the custard to prevent a skin from forming.  Set aside to cool to room temperature.

Making the Chocolate Ganache (5 minutes + cooling)

1. Pour the cream into a small saucepan and heat over medium heat until it just begins to simmer.  Remove from the heat and whisk in the chocolate until fully combined.
2. Pour the ganache into a 2-cup jug with a spout and set aside to cool to room temperature and thicken, stirring occasionally.

Assembling the Cake (15 minutes + 2 hours chilling)

1. Once the cake has fully cooled, gently peel off the parchment paper from its base.  Put the cake on a large cutting board and get down to eye level with the cake.  Using a serrated knife, slice the cake in half, turning the cake as you cut for an even slice.
2. Place the bottom half of the cake on the serving plate or cake stand and evenly spread the crème pâtissière in a thick layer on top, reserving any extra for serving.  Top with the other half of cake.
3. Slowly pour a little ganache into the middle of the cake and let it naturally spread to cover the top.  Add more ganache where necessary and smooth it with your finger or a spatula until it completely covers the top and drips a little down the sides.  You’ll probably have some extra ganache.  Rough up the ganache a little with a spatula to give it some texture, or leave it smooth.
4. Chill the cake for 2 hours before slicing and serving to allow the ganache and crème pâtissière to fully set.  Serve each piece with any leftover ganache or crème pâtissière.