Preheat the oven to 350°F.

To make the crust: In a food processor, add the graham crackers, butter, cane sugar, and cocoa. Pulse, and then mix until you have a uniform mixture and there are no chunks of graham cracker or butter.

Grease a 9-inch pie pan with butter. Transfer the graham cracker mixture to the pie pan, and lightly press it to the sides first. Use the remaining crust and press it down into the bottom of the pan.

Bake for 5 minutes or until lightly dry and set. Allow to cool completely.

In the bowl of a stand mixer fitted with the whisk attachment, add the egg yolks and cane sugar. Whisk on low for 2 to 3 minutes or until lightened in color. Add in the flour and whisk to combine completely.

Heat the milk to 140°F. Once the milk has heated, turn the mixer on low and slowly add in the warm milk into the egg mixture. Once completely combined, stop the mixer.

In a clean saucepan (do not use the one the milk was heated in, incase milk stuck to the bottom, that will burn if used without cleaning), pour in the egg mixture. Put over low/medium heat.

Continue to heat while continuously stirring with a high heat spatula by scraping the bottoms and the sides. The mixture will start to rise and may bubble, continue to stir. The mixture will start to thicken and continue to stir. The trick is to keep stirring so clumps do not form, as you want a smooth custard. If you see clumps beginning to form, stir vigorously and they will dissolve.

Continue to stir until the custard coats the spatula and does not drip off when you lift it from the pot. The whole process should take around 20 minutes. Remove the pot from heat.

To assemble the pie: In the bowl of a stand mixer fitted with the paddle attachment, add the heavy whipping cream, cane sugar, and vanilla extract. Mix on low and gradually increase the speed as the whipped cream starts to thicken, until you are full speed. Whisk until stiff peaks form.

Reserve 1/2 of the whipped cream (8 ounces or about 1 cup). Add in about half (4 ounces) of the remaining whipped cream and fold to combine, then add in the other half (4 ounces) of the remaining whipped cream and fold to combine completely.

Transfer the chocolate custard mixture to the pie crust and spread evenly. Top with the remaining 8 ounces of whipped cream. Add milk chocolate shavings on top.

Serve immediately or cover with plastic wrap and store in the fridge for up to 3 days.