Heat the oven to 325 degrees Fahrenheit. In the oven, place a rack in the centre.
Over low heat, stir the chocolate chips continuously in a double boiler.
Add the sugar, flour, and salt to a medium bowl and whisk until well combined.
Combine the eggs, buttermilk, and vanilla in a large mixing bowl. Using an electric hand mixer or whisk, mix the sugar mixture vigorously.
Combine the batter with melted chocolate using a rubber spatula.
There will be about 1 cup of leftover batter after you pour the batter into the pie crust. In the middle of the oven, place the pie.
If you insert a knife into the centre, it should come out with just a bit of moist chocolate around it. Bake for one hour and fifteen minutes to an hour and twenty-five minutes.
Cool completely after removing from the oven. Before serving, let stand for at least 1 hour.
Refrigerate the pie if not eating right away. You can serve this pie warm or chilled.
If desired, garnish the whipped cream with store-bought whipped cream just before serving.