Preheat oven to 350 degrees.
Spray a 8 or 9 inch pie plate with non-stick cooking spray. Place pie dough into prepared pie plate. Flute edges and set a side.
In a medium or small pot melt butter and chocolate over low heat stirring continuously. Add sugar and stir to combine. Turn off burner and let rest for 3 minutes.
Meanwhile, in a medium bowl whisk eggs and vanilla until well mixed. Add just a little of the chocolate mixture into the eggs to temper the eggs and not cause the eggs to scramble. Add more of the chocolate and keep whisking. Finish adding the chocolate and mix well. Pour batter into pie crust.
Bake in preheated oven on LOWER rack for 30 minutes, then move pie to TOP rack for an additional 10-15 minutes. Use a sheet of foil tented to place over pie about 1/2 way through the 10 minute time frame to keep the pie crust from over cooking.
Allow to cool completely before serving with whipped cream, if desired.
