Preheat your oven to 325°F (165°C). In a mixing bowl, combine graham cracker crumbs, granulated sugar, a pinch of salt, and melted unsalted butter. Stir until it resembles damp sand. Firmly press this mixture into the bottom of a 9-inch springform pan. Bake the crust for 8-10 minutes until set and lightly golden, then set it aside to cool.

In a large mixing bowl, beat cream cheese with an electric mixer on medium speed until creamy. Gradually add granulated sugar, mixing until smooth. Incorporate sour cream, vanilla extract, salt, and cornstarch, blending until fully combined. Add eggs, one at a time, mixing well after each addition.

Pour the cheesecake filling over the cooled crust in the springform pan. Wrap the bottom of the pan in foil to prevent water from seeping in. Place the pan in a larger baking tray filled with hot water. Bake for 50-60 minutes, until the edges are set but the center still has a slight jiggle.

Once baked, turn off the oven and crack the door open, allowing the cheesecake to rest for 1 hour. Afterward, cool it at room temperature for 1 hour before transferring it to the refrigerator. Chill for at least 4 hours or overnight.

In a saucepan, heat whole milk over medium heat until it begins to simmer. In a separate bowl, whisk together egg yolks, granulated sugar, cornstarch, and a pinch of salt. Slowly add the warm milk into this mixture while whisking constantly. Return to heat and cook until thickened, approximately 5-7 minutes while stirring. Remove from heat, whisk in butter and vanilla extract, then chill.

Spread the chilled pastry cream over the top of the cheesecake layer using a spatula for an even surface, and keep it cool in the refrigerator while preparing the ganache.

In a small saucepan, heat heavy cream over medium heat until it simmers. Pour the hot cream over chocolate chips in a bowl, letting it sit for a few minutes before stirring until smooth. Mix in butter for shine if desired.

Pour the ganache over the pastry cream layer, tilting the cheesecake for an even coating. Refrigerate until the ganache sets, about 30-45 minutes. Run a knife around the edges, release the springform pan, and slice with a warm knife for neat portions.