In a medium saucepan, heat the milk until it comes to a boil. Turn off the heat and set aside.

Using a large bowl, whisk together the egg yolks and sugar. Whisk until it thickens and is a lighter color. Sift in the cornstarch and keep whisking until the mixture is smooth and has no lumps. Slowly whisk in 1/4 cup of the hot milk. Once it's smooth, whisk in the rest of them milk.

Pour the milk/egg mixture through a strainer back into the original milk pot.

Cook the milk/egg mixture over medium-high heat. Whisk constantly until thickened. Keep cooking the custard on a low boil, but don't over boil.

Once the mixture is thick, about another 2-4 minutes of whisking at a low boil, remove the pot from the heat and stir in the butter and vanilla. Allow the custard to cool for about 2 minutes and cover with plastic wrap. Allow the plastic wrap to touch the top of the custard to prevent a "skin" from forming. Chill the custard in the refrigerator.

Preheat oven to 350℉, and spray an 8" round pan with butter and flour. Line the bottom with a piece of parchment paper and grease again. Set aside.

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

In a large standing electric mixer, beat the eggs and sugar until pale colored and fluffy (4-5 minutes).

Then, in a small saucepan, heat together the milk and butter until steamy. Stir in the vanilla.

Slowly beat the flour mixture into the egg and sugar mixture. Slowly beat in the milk mixture until the batter is well mixed. It will be a bit bubbly and look like pancake batter. Scrape the sides and fold the batter a few more times. Then pour the batter into the prepared cake pan.

Bake for 35 minutes, or until a toothpick comes out clean. Cool in the pan ten minutes and then remove to a wire rack. Cool completely.

Once the cake is cool, cut it horizontally. Put the bottom half on a serving plate and spread the chilled cream over the cake, leaving a 1" border around the edges. Top with the second half of the cake and press down so the cream makes its way to the edge. Cover the cake and chill for at least three hours, or overnight. Add the ganache before serving.

About ten minutes before serving, melt the cream and the chocolate in the top of a double boiler and stir until melted. Set aside for 3 minutes, then whisk the mixture until smooth. Pour over the cake, allowing it to spread over the edges. Serve immediately.