Preheat oven to 350 degrees Fahrenheit.
Combine crushed chocolate graham crackers with melted butter and press into the bottom of a greased nine-inch springform pan.
Bake the crust for ten minutes, then remove and cool completely.
Cream the softened cream cheese and sugar together until completely smooth and free of lumps.
Add the sour cream and vanilla extract, beating on low speed until incorporated.
Sift in the cocoa powder and mix until combined.
Add eggs one at a time, mixing on low speed just until incorporated.
Pour filling over the cooled crust.
Place the pan in a water bath and bake until the edges are set but the center remains slightly wobbly.
Cool the cheesecake in the oven with the door propped open for one hour.
Chill in the refrigerator for at least 6 hours before serving.