Cream together the Granulated Sugar (3/4 cup) and Butter (1/2 cup). Add the Egg (2) and Vanilla Extract (2 teaspoon). Combine thoroughly.
Mix the All-Purpose Flour (1 1/2 cup), Baking Powder (1 1/2 cup), Corn Starch (1 tablespoon), and Salt (1/4 teaspoon). Add them to the wet mixture. Whisk until incorporated.
Stir in the Milk (1/2 cup) and pour the batter 3/4 high into the cups of a greased muffin tin. Bake the cupcakes at 350 degrees F (180 degrees C) for 18-20 minutes or until a toothpick inserted in the center comes out clean.
Separate Egg (2) Yolks and set aside.
To make the custard, add the Granulated Sugar (1/4 cup) to the saucepan. Follow it with Whole Milk (1 cup), Egg Yolks, Corn Starch (1 tablespoon) and Vanilla Extract (1 teaspoon). Whisk together the ingredients until well combined. Over medium heat, stir the custard constantly for 3-8 minutes or until thick. Strain the thickened custard into a bowl to prevent any lumps. Chill covered with plastic wrap in the fridge.
Heat the Heavy Cream (4 fluid ounce) and add the Semi-Sweet Chocolate Chips (4 ounce). Let sit for several minutes, then stir to combine.
Take a cupcake and cut in half. Spread some of the custard in a layer and replace the top of the cupcake. Add a dollop of the chocolate ganache to the top. Repeat with the other cupcakes.