Preheat the oven to 350°F (175°C).

In a mixing bowl, cream the butter and sugar until light and fluffy.

Beat in the eggs one at a time along with the vanilla extract.

In another bowl, whisk together the flour, baking powder, and salt.

Alternately add the milk and dry ingredients to the butter mixture, starting and ending with the dry ingredients.

Divide the batter evenly between the prepared cake pans and bake for 25-30 minutes until a toothpick inserted into the center comes out clean.

In a saucepan, heat the milk and vanilla extract until steaming.

In another bowl, mix the eggs, sugar, cornstarch, and salt until smooth.

Slowly whisk the hot milk into the egg mixture, then return to the saucepan and cook until thickened.

Heat the heavy cream until steaming, then pour it over the chocolate chips and stir until smooth.

Once the cakes are cool, place one layer on a serving plate, spread the custard filling evenly, and top with the second cake layer.

Pour the chocolate ganache over the top of the cake, allowing it to drip down the sides.

Refrigerate the cake for at least an hour to set the ganache.