To make the pastry cream:

1. Put the egg yolks in a medium sized bowl and gently beat them together. Set aside.
2. Add the sugar and cornstarch to a large saucepan and whisk together until no more lumps of cornstarch remain, then add the milk.
3. Cook, stirring continuously, over medium heat until mixture just begins to thicken and simmer. Be careful not to boil it.
4. Add a little bit of the milk mixture to the egg yolks and quickly whisk together, then add the egg mixture to milk mixture, putting it all back in the pan. This process ensures that you don’t cook the egg yolks too quickly and get scrambled eggs.
5. Place the pan back on the heat and bring to a light boil. You should see large bubbles popping on top. Allow to boil for 1 minute, stirring continuously. Don’t boil for too long, or you can overcook it and it’ll actually break down, rather than get thicker.
6. Remove from heat and add the butter and vanilla extract. Stir until smooth, then pour into a bowl and cover with clear wrap pressed against the top so that it doesn’t get a film on top. If you find your cream is lump, you can strain it. Set in the fridge to cool completely, 1-2 hours.

To make the cake layers:

1. Prepare two 9-inch cake pans with parchment paper circles in the bottom and grease the sides. Preheat oven to 350°F (176°C).
2. Combine flour, baking powder and salt in a medium sized bowl. Set aside.
3. Add the eggs, sugar and vanilla extract to a large mixer bowl and whip on high speed until pale, fluffy and thickened, about 4 minutes.
4. While the eggs are whipping, heat the milk and butter until the butter is melted and the mixture is very hot. It doesn’t have to be boiling, but it should be very hot.
5. Add half of the dry ingredients to the whipped egg mixture and gently fold together until mostly combined. Add the remaining dry ingredients to the egg mixture and gently fold together until just well combined.
6. Add the hot milk mixture to the batter and gently whisk together until well combined.
7. Divide the batter evenly between the prepared cake pans and bake for 20-23 minutes, or until a toothpick inserted in the middle of the cakes comes out clean.
8. Remove the cakes from the oven and allow to cool for 2-3 minutes, then remove to a cooling rack to finish cooling.

To finish off the cake:

1. When the pastry cream and cakes have cooled completely, make the chocolate glaze. Add the chocolate chips and corn syrup to a medium size bowl.
2. Heat the heavy whipping cream just until it begins to boil, then pour over the chocolate chips and corn syrup. Allow to sit for 1-2 minutes, then stir until smooth.
3. Remove the domes from the tops of the cakes and place one cake on a serving platter. Give the pastry cream a stir to smooth it out, then spread the pastry cream over the cake layer, leaving about an inch between the cream and the side of the cake for it to spread a bit, then top it with the second cake layer. 
4. Pour the chocolate over the top of the cake and spread it out towards the edges, letting some of the chocolate drip down the sides.
5. Refrigerate cake until ready to serve. Store in an air-tight carrier, if possible. The cake is best if eaten within 3-4 days.