01 -
Prepare and bake the yellow cake mix according to package directions for cupcakes. Let them cool completely.
02 -
In a saucepan, whisk together milk, sugar, cornstarch, and egg yolks. Cook over medium heat, whisking constantly, until thickened and bubbling. Remove from heat and stir in butter and vanilla. Cover with plastic wrap touching the surface and chill until cold.
03 -
Once cupcakes are cool, use a paring knife or cupcake corer to remove a small center from each cupcake. Fill with chilled pastry cream using a piping bag or spoon.
04 -
Heat heavy cream in a small saucepan just until simmering. Remove from heat and pour over chopped chocolate. Let sit for 2 minutes, then stir until smooth.
05 -
Spoon ganache over the tops of filled cupcakes and let set slightly before serving.