To make the Vanilla custard: In a small bowl, whisk together the sugar, cornstarch and salt.
Whip egg yolks in a separate bowl, then whisk into the sugar mixture.
To a heavy bottomed saucepan add the half and half and butter. Heat over medium-high heat until the butter has melted.
Gradually whisk the sugar-egg mixture into the half and half and bring to a boil. Whisk constantly for 1-2 minutes or until thickened.
Remove from the heat and add the vanilla whisking until combined.
Pour the custard into a bowl, and press plastic wrap on top. Chill just until it's warm but, still pourable around 45 minutes.
To make the ganache Melt the chocolate chips together with the cream until smooth. Melt in a double boiler, or in the microwave in 20 second increments stopping to stir each time. Cool until slightly warm to the touch and the thickness of a pourable pudding.
To assemble: Divide the doughnuts, custard and ganache into thirds. Layer, beginning with doughnuts, drizzle with chocolate and spread with custard. Repeat.
For the third layer, start with doughnuts, top with custard and end with chocolate ganache on top.
Cover and chill until serving.