No Bake Double Chocolate Pie

Make the crust: 
0 Place the cookies in a food processor and pulse until very fine crumbs form. Melt the portion of the butter for the crust in the microwave and pour over the cookies. Pulse again a few times until evenly combined. Spray a 9"x9" pie tin with nonstick cooking spray. Press the chocolate crust evenly into the pie tin.
Make the filling: 
1 Combine the sugar, cornstarch, egg yolks and salt in a medium saucepan. Stir with a whisk a few times to combine (the mixture will be quite dry).
2 Place the pan over medium-high heat. When the pan is hot, slowly add the milk while whisking. Bring the mixture to a simmer, whisking continuously. Simmer until the mixture forms a thick custard that easily coats the back of a spoon, 4 to 5 minutes. (The transition from thin to thick custard-like consistency happens very fast and is easy to see. Just make sure not to stop whisking as the filling heats so you won't miss this transition.)
3 Remove the pan from heat and stir in the unsweetened chocolate, butter and vanilla extract. Stir until the chocolate is melted and evenly incorporated.
4 Pour the filling over the pie crust.
5 Cool pie on a wire rack for 1 hour (don't skip this step; if it cools too quickly, the filling will crack). Refrigerate for at least 3 hours and up to 3 days.
6 Just before serving, finish the pie with a drizzle of melted milk chocolate, fresh berries or whipped cream. Slice and enjoy!