Preheat the oven to 350°F (175°C) and grease two round cake pans.

In a bowl, whisk together flour, baking powder, and salt. Set aside.

In another bowl, cream softened butter and sugar until fluffy. Add eggs one by one, then mix in milk and vanilla.

Gradually combine dry ingredients with wet until just mixed. Divide batter between prepared pans.

Bake for 25–30 minutes or until a toothpick comes out clean. Cool in pans for ten minutes before transferring to wire racks.

For custard, heat milk, sugar, cornstarch, and egg yolks in a saucepan over medium heat; stir until thickened. Remove from heat, then stir in butter.

Assemble the pie by placing one layer on a serving plate, spreading custard on top, then adding the second layer.

For ganache, melt chocolate chips with heavy cream over low heat until smooth; pour over the assembled cake.