Preheat oven to 350°F (175°C).
In a medium saucepan over low heat, melt chocolate chips and butter, stirring until smooth.
Remove from heat and whisk in sugar, eggs, and vanilla until combined.
Stir in flour and salt until just mixed.
Pour batter into the prepared pie crust and smooth the top.
Bake for 25-30 minutes or until set but still slightly gooey in the center.
Cool slightly before slicing. Serve with whipped cream or ice cream if desired.