Make Coconut-Pecan Topping: While the pie cools, prepare the topping. In a medium saucepan over medium heat, combine the packed brown sugar, heavy whipping cream, and 1/4 cup chopped butter. Bring the mixture to a boil, stirring often, until the sugar has completely dissolved. Remove from heat.
Temper Egg Yolks & Finish Topping: In a small bowl, whisk the 2 large egg yolks. Gradually add a small amount (about 1/4 cup) of the hot brown sugar mixture to the egg yolks, whisking constantly to temper them. Then, slowly pour the tempered egg yolk mixture back into the saucepan with the remaining hot brown sugar mixture, whisking constantly to prevent the eggs from scrambling. Cook again over medium heat, stirring constantly, until the mixture thickens, about 2-3 minutes. Do not boil vigorously. Remove from heat and stir in the flaked coconut and 1 teaspoon vanilla extract. Let the topping cool for 10 minutes.
Assemble Pie & Chill: Pour the cooled coconut-pecan topping evenly over the chocolate filling in the pie. Sprinkle with the 1/4 cup chopped pecans. Chill the pie in the refrigerator until it is completely cold and set, at least 4 hours, or preferably overnight.
Slice and Serve: Slice, serve, and enjoy your rich German Chocolate Pie!
