Preheat oven to 325℉

In a double boiler, melt the chocolate

In a mixing bowl, cream together the cream cheese and sugar. Add the eggs one at a time and blend well. Slowly add the chocolate until mixed, then add the vanilla and sour cream

Pour into pie crust, and bake for 45-50 minutes in preheated oven or until cake jiggles evenly across the top when lightly shaken

Let cool on the counter and refrigerate when cooled enough