Step 1: Preheat oven to 350°F (175°C). Place pie crust in a 9-inch pie dish and set aside.
Step 2: In a microwave-safe bowl, melt chocolate chips in 30-second intervals, stirring until smooth. Set aside to cool slightly.
Step 3: In a large bowl, cream together 1/2 cup butter and granulated sugar until light and fluffy. Beat in 2 eggs and vanilla extract.
Step 4: Stir in melted chocolate until well combined. Mix in flour and salt until just incorporated.
Step 5: Pour chocolate filling into the prepared pie crust. Bake for 25 minutes.
Step 6: While pie bakes, prepare topping: In a medium saucepan, combine coconut, pecans, evaporated milk, brown sugar, 1/4 cup butter, and egg yolk. Cook over medium heat, stirring constantly, until thickened (about 10 minutes).
Step 7: Remove pie from oven after 25 minutes. Spread coconut-pecan topping evenly over the partially baked filling.
Step 8: Return pie to oven and bake for an additional 15 minutes, or until topping is golden and set.
Step 9: Cool pie completely on a wire rack before serving (at least 2 hours).