Preheat oven to 350°F (175°C) and grease two 9-inch round cake pans. Line the bottoms with parchment paper.

In a bowl, sift together flour, baking powder, and salt.

In another bowl, beat eggs and sugar with a mixer until thick and pale.

Heat milk and butter until melted. Add vanilla. Slowly fold into egg mixture.

Gently fold in dry ingredients until just combined.

Divide batter between the pans and bake for 20–25 minutes until golden and a toothpick comes out clean. Let cool completely.

For the pastry cream, heat milk and half the sugar until just boiling.

Whisk egg yolks, remaining sugar, and cornstarch in a bowl.

Slowly add hot milk into the egg mixture while whisking to temper.

Return mixture to pan and cook over medium heat until thick.

Remove from heat, stir in butter and vanilla. Cover with plastic wrap and refrigerate until cool.

For ganache, heat cream in a saucepan until steaming. Pour over chocolate and butter. Let sit, then stir until smooth.

Place one cake layer on a serving plate. Spread pastry cream evenly. Top with second cake layer.

Pour ganache over the top and allow it to drip down the sides.

Chill for at least 1 hour before serving.