For the Crust:

1. Preheat your oven to 350°F (175°C).
2. Combine the chocolate graham cracker crumbs, sugar, and melted butter in a medium bowl. Mix until the crumbs are evenly coated.
3. Press the mixture into the bottom of a 9-inch springform pan. Bake for 10 minutes, then set aside to cool.

For the Cheesecake Filling:

1. Reduce the oven temperature to 325°F (163°C).
2. In a large bowl, beat the cream cheese and sugar until smooth and fluffy.
3. Add the sour cream and vanilla extract, mixing until combined.
4. Beat in the eggs one at a time, mixing just until incorporated.
5. Stir in the melted chocolate until evenly combined.
6. Pour the filling over the prepared crust and smooth the top.
7. Bake for 55-65 minutes, or until the edges are set but the center is slightly jiggly.
8. Turn off the oven, crack the door slightly, and let the cheesecake cool inside for 1 hour. Then, transfer to the fridge to chill for at least 4 hours or overnight.

For the Coconut-Pecan Topping:

1. In a medium saucepan, melt the butter over medium heat.
2. Stir in the evaporated milk, sugar, and beaten egg yolks. Cook, stirring constantly, until the mixture thickens (about 8-10 minutes).
3. Remove from heat and stir in the vanilla, shredded coconut, and chopped pecans. Let the topping cool to room temperature.

To Assemble:

1. Spread the cooled coconut-pecan topping over the chilled cheesecake.
2. Garnish with additional chocolate shavings or pecans if desired.
3. Slice and serve chilled.