Preheat the oven to 350°F.

In a large bowl, combine the crushed chocolate sandwich cookies, sugar, and melted butter. Press the mixture evenly onto the bottom and about 1 inch up the sides of a 9-inch springform pan.

Bake the crust for 8 minutes. Remove from the oven and set aside while preparing the cheesecake.

Melt the 10 ounces of semi-sweet chocolate in the microwave or in a double boiler until smooth. Set aside to cool slightly.

In the bowl of a stand mixer fitted with the paddle attachment, beat the cream cheese and sugar on medium speed until smooth, scraping down the sides of the bowl as needed.

Reduce the mixer speed to low. Add the sour cream and cocoa powder and mix until combined, scraping down the sides as needed.

Add the melted chocolate and mix until incorporated. Add the eggs one at a time, mixing on low speed after each addition just until combined. Do not overmix.

Pour the cheesecake filling over the prepared crust and spread evenly.

Double-wrap the bottom of the springform pan with aluminum foil, making sure the foil is tightly sealed to keep water from getting into the pan.

Place the springform pan in a larger roasting pan. Carefully pour very hot water into the roasting pan until it reaches about ¾ inch up the sides of the springform pan. Make sure the water does not come above the foil.

Bake for 60–70 minutes, or until the edges are set and the center still has a slight jiggle.

Carefully run a thin knife around the edge of the cheesecake to loosen it from the pan. Allow the cheesecake to cool at room temperature for at least 1 hour.

Place the chopped chocolate and heavy cream in a small microwave-safe bowl. Microwave in short intervals, stirring between each, until smooth. Alternatively, heat the chocolate and cream together in a small saucepan over low heat, stirring until smooth.

Spread the ganache evenly over the cooled cheesecake.

Cover the springform pan and refrigerate the cheesecake for at least 6 hours, preferably overnight.

Before serving, carefully release the sides of the springform pan and slice the cheesecake.