Preheat the oven to 325°F (160°C). Grease the springform pan and line the bottom with parchment paper for easy removal.

In a mixing bowl, combine the graham cracker crumbs, melted butter, and sugar. Mix until well combined. Press the mixture into the bottom of the prepared springform pan to form the crust. Set aside.

In another mixing bowl, beat the softened cream cheese with an electric mixer until smooth and creamy. Gradually add the sugar and continue to beat until fully incorporated.

Add the eggs, one at a time, mixing well after each addition. Then, add the vanilla extract, sour cream, cocoa powder, and melted chocolate. Mix until all ingredients are well combined and smooth.

Pour the cheesecake batter over the prepared crust. Bake in the preheated oven for about 60 minutes, or until the center is set but still slightly jiggly. Turn off the oven and leave the cheesecake inside for another hour.

While the cheesecake is cooling, prepare the topping. In a saucepan over medium heat, combine the sugar, evaporated milk, butter, and egg yolks. Cook while stirring until the mixture thickens, about 10 minutes.

Remove the saucepan from heat and stir in the shredded coconut, chopped pecans, and vanilla extract. Allow the topping to cool slightly.

Once the cheesecake has cooled, spread the coconut-pecan topping evenly over the top. Refrigerate for at least 4 hours, preferably overnight, to allow the flavors to meld and the cheesecake to set.

Before serving, carefully remove the sides of the springform pan. Slice and serve chilled.