Step 1: Make the Crust
Mainly, start by combining the graham cracker crumbs, brown sugar, and melted butter in a medium-sized bowl. Mix thoroughly until the crumbs are evenly coated. Press this mixture into a 9-inch pie plate, ensuring it’s densely packed. Bake at 325°F for 8-10 minutes, then let it cool completely before moving on to the next step.

Step 2: Prepare the Pudding
In a medium saucepan, whisk together the milk, sugar, and cocoa powder. Heat over medium-low heat until warm. While the milk heats, gently whisk the egg yolks in a small bowl. Temper them by adding a few tablespoons of the warm milk, then pour the tempered yolks back into the saucepan. Next, create a slurry by mixing a couple of tablespoons of the warm milk with the cornstarch, then incorporate it back into the pudding mixture. Continue cooking, stirring constantly, until the pudding thickens enough to coat the back of a spoon.

Once thickened, remove the saucepan from the heat and slowly stir in the chopped dark chocolate until it melts completely. Add the vanilla extract, strain the pudding through a fine sieve, and transfer it to the prepared crust. Cover the surface with plastic wrap, pressing it directly onto the pudding to prevent a skin from forming. Poke a few holes in the wrap and refrigerate for 2-4 hours until firm.

Step 3: Whip the Cream
When the pudding is fully chilled, prepare the whipped cream. Chill a mixing bowl in the freezer for 10 minutes, then beat the heavy cream until soft peaks form. Gradually add the powdered sugar and continue beating until stiff peaks develop. Spread the whipped cream over the pudding and garnish with chocolate shavings if desired.