1. Make the Pastry Cream:

2. 1. Heat the milk in a saucepan until it just begins to boil, then remove from heat.

3. 2. In a separate bowl, whisk yolks and sugar until light and thickened.

4. 3. Sift in cornstarch and whisk until smooth.

5. 4. Slowly temper with a bit of the hot milk, whisking constantly.

6. 5. Add remaining milk, strain, then return to pot.

7. 6. Cook over medium-high heat until thickened and boiling.

8. 7. Remove from heat, stir in butter, and let cool.

9. 8. Cover with plastic wrap touching the surface and chill.

10. Make the Sponge Cake:

11. 1. Preheat oven to 350°F. Prepare an 8-inch round cake pan with spray and parchment.

12. 2. Whisk together flour, baking powder, and salt.

13. 3. Beat eggs and sugar for about 4 minutes until fluffy.

14. 4. Heat milk and butter together until melted and steaming.

15. 5. Slowly add dry ingredients to egg mixture.

16. 6. Stir vanilla into milk-butter mixture, then slowly pour into batter.

17. 7. Mix until combined, pour into pan.

18. 8. Bake for about 33 minutes, until toothpick comes out clean.

19. 9. Cool for 10 minutes in pan, then transfer to wire rack.

20. Assemble the Cake:

21. 1. Slice cake horizontally into two layers.

22. 2. Spread chilled pastry cream over the bottom half.

23. 3. Place top cake layer and gently press down.

24. 4. Chill cake for 2+ hours or overnight.

25. Make the Ganache:

26. 1. Heat cream until steaming.

27. 2. Add chopped chocolate and let sit 5 minutes.

28. 3. Stir until smooth, then pour over the chilled cake.