Preheat oven to 450'F
Bake pie crust for about 8 minutes, or until just golden.
In a large mixing bowl cream the butter and sugar together with a hand mixer until smooth.
In a small sauce pan bring the heavy cream to a scald. Pour 8 ounces of your 10 ounce chopped chocolate into the scalded cream. Add vanilla to cream chocolate mixture and stir until completely melted.
Meanwhile in a small bowl, whisk eggs yolks until smooth. Then add your flour to your egg yolks one 1/2 tablespoon at a time until completely smooth.
With a whisk, slowly pour hot chocolate cream mixture into the egg yolk mixture, whisking the entire time! (The hot chocolate and cream will cook the egg yolks. Whisking will keep the yolks from clumping and making you an omelet..eww!)
Let chocolate egg yolk mixture to cool completely!!!! (Can not emphasis this more. Pop it in the freezer for 10 minutes if you have to, just make sure it isn't hot!)
Pour chocolate mixture into butter sugar mixture and beat with a hand mixer on high for 4-5 minutes. This is your chocolate custard!!! :-D
Spread your chocolate custard filling into the 9 inch pie crust.
Top the filling with the remaining chopped chocolate.
Spoon whipped topping on top of the filling and spread out evenly.
I dusted the top of the pie with cocoa powder because it was pretty!
Chill for 3 hours before serving. (Again, I froze the pie. If you like frozen custard, this pie rocks frozen!!! Just a little harder to cut.)