Pre heat oven to 350 degrees and place rack on lowest shelf in oven.
Prepare pie crust according to directions. See recipe notes.
Make filling:
Melt butter in a small pan. Remove from heat.
Add sugar and vanilla, whisk until mixed well.
Whisk in two beaten eggs to butter mixture.
Add cocoa powder, chopped chocolate and flour to pan. Fold in until wet and dry ingredients are incorporated. This will take just a few turns of the spatula, do not over mix!
Scrape brownie filling into prepared unbaked pastry shell.
Bake for 35-40 minutes.
Let sit on counter for at least one hour before serving.
Notes
-Use a 9 inch shallow pie plate for this recipe. Do not use a deep dish pie plate. -If you would like to add nuts, add 1 cup of roughly chopped nuts to the batter with the flour and reduce the cooking time to 35 minutes. -I highly suggest baking on the bottom rack of the oven (not the bottom of the oven, the bottom rack). Place the rack on the lowest shelf setting of the oven. This will insure the bottom crust is cooked without the top of the pie getting overcooked.