Begin preheating the oven to 325° F (163° C). On a baking sheet, lay out a silicone baking mat or a piece of parchment.
In a medium size bowl, whisk the egg white and the sugar together until a bit frothy and foamy. Add the pecans, stir gently, then spread the pecans out over the lined baking sheet. Bake for about 20-25 minutes, until the scent really fills the air, turning the pecans about every 10 minutes.
Remove from the oven and cool.
Pudding:
In a medium sized saucepan, add the cream, milk, and butter. Set the pan over medium heat.
In a medium sized bowl, add the eggs, granulated sugar, cornstarch, cocoa powder, and salt. Whisk the ingredients together until thoroughly combined.
Once the cream mix has warmed (steam rising but not boiling), slowly ladle spoonfuls into the egg mixture while whisking constantly to temper. Add about a third or half of the cream total.
Strain the egg mixture back into the saucepan using a fine mesh sieve, place the saucepan over medium heat while whisking constantly. Once the pudding has thickened, remove the pan from the heat and add the vanilla and chopped chocolate. Whisk until thoroughly melted.
Serve with pecans atop.
Both can be made ahead of time. Store the pecans in an airtight container. Store the pudding covered with plastic wrap on the surface in the refrigerator and reheat as necessary.