Step 1

First, preheat the oven to 350.

Step 2

Pulse the graham crackers, melted butter, cinnamon and sugar in a food processor. Alternatively, you can crush them in a plastic storage bag. Make sure the crumbs are very fine. Press the mixture into the pie tin, using the bottom of a glass or small measuring cup to pack the crumbs firmly. Press the crust up the edges of the pie tin.

Step 3

Bake on a cookie sheet for 10 minutes. Let cool while you make the chocolate filling.

Step 4

Sift the sugar, cocoa powder and corn starch into a small bowl. Add 1/2 cup of the milk and whisk vigorously until the mixture is very smooth and free of lumps. Slowly add the rest of the milk while whisking constantly. Finally, whisk in the egg yolk.

Step 5

Pour the mixture into a small pan and bring to a simmer over medium heat. Stir the mixture constantly with a wooden spoon, being sure to scrape the corners of the pan with the spoon. Once the mixture starts to thicken and simmer, turn the heat to low and continue cooking for 1 minute. The mixture should be silky and slightly thickened—it will firm up in the crust later.

Step 6

Remove the pan from the heat and add the butter. Stir to melt, then stir in the vanilla. Pour the pudding into the crust. Press plastic wrap against the surface of the pudding and chill in the fridge for at least 4 hours or overnight.

Step 7

When ready to serve, whip the heavy cream, sugar, and vanilla together until a thick whipped cream forms. Spread evenly on top of pie. Slice and serve.