In a large saucepan, whisk together the granulated sugar and cornstarch.

In a separate bowl, whisk together the eggs and whole milk until well combined.

Gradually pour the egg mixture into the saucepan with the sugar and cornstarch, whisking constantly to prevent lumps from forming.

Place the saucepan over medium heat and cook, stirring constantly, until the mixture thickens and comes to a boil.

Once the mixture has thickened, remove it from the heat and stir in the vanilla extract.

Transfer the mixture to a heatproof bowl and cover the surface with plastic wrap to prevent a skin from forming. Let it cool to room temperature.

Once the custard has cooled, whip the heavy cream until stiff peaks form. Gently fold the whipped cream into the custard until well combined.

Line the bottom of a 9x13-inch baking dish with a single layer of graham crackers.

Spread half of the custard mixture over the graham crackers, smoothing it out into an even layer.

Add another layer of graham crackers on top of the custard layer.

Spread the remaining custard mixture over the second layer of graham crackers.

Finish by adding a final layer of graham crackers on top of the custard.

In a microwave-safe bowl, heat the chocolate chips in 30-second intervals until melted, stirring between each interval.

Pour the melted chocolate over the top layer of graham crackers, spreading it out evenly.

Cover the baking dish with plastic wrap and refrigerate for at least 4 hours, or overnight, to allow the cake to set.