Begin by crushing chocolate sandwich cookies into fine crumbs using a food processor. In a mixing bowl, combine crumbs with melted unsalted butter, stirring until fully coated. Press the mixture firmly into the bottom of a 9-inch springform pan to form a solid crust. Chill in the refrigerator for at least 15 minutes to set.

In a large mixing bowl, beat softened cream cheese with an electric mixer on medium speed until completely smooth. Gradually add in melted and cooled semi-sweet chocolate chips, followed by powdered sugar and vanilla extract, blending until well combined. In a separate bowl, whip heavy cream until stiff peaks form, then gently fold this whipped cream into the chocolate mixture. Spread the filling evenly over the chilled crust.

In a medium saucepan, whisk together evaporated milk, granulated sugar, and beaten egg yolks over medium heat. Stir constantly until the mixture thickens, about 5-7 minutes. Once thickened, remove from heat and mix in shredded coconut, chopped pecans, and a splash of vanilla extract. Allow the topping to cool slightly before spreading it over the cheesecake filling.

Return the layered cheesecake to the refrigerator and chill for at least 4 hours, or preferably overnight, to allow the flavors to meld and the filling to set completely.

If adding a chocolate ganache, heat heavy cream in a small saucepan until it just begins to boil. Pour this hot cream over semi-sweet chocolate chips in a heatproof bowl, letting it sit for about 5 minutes. Stir until smooth and glossy, then drizzle it over chilled cheesecake.