Step 1: Preheat oven to 350°F (175°C). Grease a 9-inch springform pan. Combine chocolate cookie crumbs and melted butter. Press firmly into the bottom of the prepared springform pan. Bake for 8-10 minutes. Let cool slightly.
Step 2: Reduce oven temperature to 325°F (160°C). Wrap the bottom of the springform pan tightly with heavy-duty foil to prevent water bath leakage.
Step 3: For the filling, in a large bowl, beat softened cream cheese with granulated sugar until smooth and creamy, about 2-3 minutes. Add cocoa powder and vanilla extract, mixing until just combined.
Step 4: Beat in eggs one at a time, mixing on low speed until just incorporated after each addition. Do not overmix. Gently fold in the sour cream or heavy cream until smooth. Pour the cheesecake filling over the cooled crust.
Step 5: Place the springform pan in a larger roasting pan. Fill the roasting pan with hot water to reach about halfway up the sides of the springform pan (creating a water bath).
Step 6: Bake for 60-70 minutes, or until the edges are set but the center still jiggles slightly. Turn off the oven, prop the door open slightly, and let the cheesecake cool in the water bath for 1 hour. Remove from water bath, remove foil, and cool completely on a wire rack.
Step 7: Once cooled, refrigerate the cheesecake for at least 4-6 hours, or preferably overnight, until thoroughly chilled and set.
Step 8: For the coconut-pecan topping, in a medium saucepan, combine evaporated milk, granulated sugar, butter, and egg yolks. Cook over medium-low heat, stirring constantly, until the mixture thickens (about 8-10 minutes). Do not boil.
Step 9: Remove from heat and stir in vanilla extract, sweetened shredded coconut, and toasted pecans. Let the topping cool completely before spreading.
Step 10: Once the cheesecake is fully chilled, evenly spread the cooled coconut-pecan topping over the top. Serve and enjoy!