Mix the graham crackers, granulated sugar, butter, and cocoa. Press the mixture onto the bottom and up the sides of a 9 inch springform pan. Set crust aside.
Beat the cream cheese until smooth. Gradually add sweetened condensed milk; beat well. Add vanilla and eggs, and beat on medium speed until smooth. Mix half the chocolate chips into the cream cheese mixture. Pour into prepared crust. Sprinkle the top with remaining chocolate chips.
Bake at 300°F for one hour. Turn off the oven (DO NOT OPEN OVEN DOOR) and leave the cake in the oven to cool for another hour. Remove the cheesecake from the oven to a wire rack and cool completely.
Refrigerate until cold throughout the dessert before removing the sides of the pan. Keep cake refrigerated until time to serve.
Notes
For best results, do not skip leaving the cheesecake to cool in the oven for one hour without opening the door (I know it's tempting to peek, but don't!). Then, allowing additional time on the counter at room temperature before transferring it to the fridge.