Position rack in lower third of the oven; preheat to 350°F.
To make the crust: Blend peanuts, sugar, graham cracker crumbs, and butter in mixing bowl until moistened. Spread in a 9-inch pie plate, using the bottom of a glass to press evenly over the bottom and up the sides. Bake until crust begins to set and colors slightly (12-14 minutes). If it puffs up while baking, press gently with the back of a fork.
Remove from oven, sprinkle chopped chocolate over bottom, and let soften for 1-2 minutes. With a pastry brush or back of a spoon, spread chocolate evenly all over. Cool, then chill until chocolate sets (about 30 minutes).
To make the filling: Whisk sugar, cocoa, cornstarch, and salt in a heavy medium saucepan. Add 3 TBSP of milk; whisk into a smooth paste. Whisk in remaining milk. Cook over medium heat, stirring constantly with a wooden spoon or spatula, scraping sides, until it thickens and bubbles at edges (about 5-8 minutes). Continue to cook and stir for 1 minute; add chocolate and stir briskly until melted and pudding is smooth (30 seconds more). Remove from heat; stir in vanilla. Scrape into crust and level it with a spatula. Let cool for 1 hour, then refrigerate. Once filling is cool, cover and chill for several hours, or overnight. Top with Classic Whipped Cream; sprinkle with peanuts, if desired.