• Have ready a fully baked pie crust. You can make it from scratch or buy a frozen one and bake as directed. You can also use a crumb crust, though I've only tested with pastry crust so far.
• Put the unsweetened chocolate in one large mixing bowl and the milk chocolate in another, preferably a medium size or slightly smaller so you can tell the two mixtures apart.
• In a 3 quart saucepan, off heat, whisk together the sugar, gelatin, cornstarch, and cocoa powder. Whisk in the egg yolks and 1 cup of the milk until smooth, then gradually whisk in the remaining milk.
• Set the saucepan over medium low heat and whisk continuously until mixture thickens and boils. This shouldn't take longer than 10 minutes, so if it's not thickening just slowly increase the heat. Once mixture thickens and begins to boil, whisk and boil continuously for another 1 ½ minutes. In theory this is supposed to destroy the amylase in the egg yolks, which breaks the cornstarch bond and causes pies to become runny later. Not sure how much it matters here, but I do it anyway.
• Set the bowl of milk chocolate on the scale and set tare to zero. Pour in custard mixture (while still hot) until it reads 8 oz. If you aren't using a scale, just measure out 1 cup of custard mixture and pour it into the bowl with the milk chocolate.
• Pour the remaining custard mixture into the bowl with the unsweetened dark chocolate.
• Add 1 teaspoon of the butter to the milk chocolate mixture and remaining 2 teaspoons to the dark chocolate mixture.
• To each bowl, add ½ teaspoon of vanilla and a pinch of salt and whisk until chocolate is melted and mixture is smooth.
• Let cool at room temperature for about 45 minutes, whisking once or twice to help it cool down. Between whiskings, keep the tops covered with a piece of wax or parchment paper directly over the pudding. This should help keep a skin from forming. The goal is for the mixtures to be cool enough not to melt the whipped cream.
• In a mixing bowl, whip ¾ cup (6 oz) of cream until stiff peaks just start to form.
• Give the chocolate mixtures another good whisk and make sure they're cool enough to fold the cream into. Fold half of the whipped cream into the dark chocolate mixture and the other half of the whipped cream into the milk chocolate mixture. The milk chocolate mixture should be lighter in color and texture.
• Scrape the dark chocolate mixture into the baked pie shell, then scrape the milk chocolate mixture on top. Cover with a sheet of waxed paper or plastic wrap and chill for at least 4 hours or until gelatin has set and it feels firm enough to cut.

Topping

• Once set, whip the remaining 8 oz of cream and sweeten to taste with confectioners's sugar. You can also skip this step and use Cool Whip if you want.
• Pipe the remaining whipped cream over the top (or just spread it) and crumble cookies in the center. You can serve it right after garnishing, but I recommend putting the whole pie in the freezer, letting freeze until firm, then cutting while partially frozen. The gelatin prevents it from solidifying completely.