Preheat your oven to 350°F (175°C). Wrap the outside of a 9-inch springform pan with two layers of heavy-duty aluminum foil. This will create a waterproof seal for the water bath.

In a food processor, pulse the chocolate sandwich cookies into fine crumbs. If you don't have a food processor, place them in a zip-top bag and crush them with a rolling pin.

In a medium bowl, combine the cookie crumbs and melted butter. Mix until all the crumbs are moistened. Press the mixture firmly and evenly into the bottom of the prepared springform pan. Bake for 10 minutes. Set aside to cool while you prepare the filling.

Reduce oven temperature to 325°F (165°C).

In a large bowl using an electric mixer, beat the softened cream cheese on medium speed until completely smooth and free of lumps, about 2-3 minutes. Scrape down the sides and bottom of the bowl.

Add the granulated sugar and beat until smooth. Add the eggs one at a time, mixing on low speed just until each is incorporated. Do not overmix. Stir in the sour cream and vanilla extract.

Transfer half of the cheesecake batter (about 3 cups) to a separate medium bowl.

To the first bowl, add the creamy peanut butter. Mix on low speed until just combined. Pour this peanut butter layer evenly over the pre-baked crust.

To the second bowl of batter, add the melted semi-sweet chocolate and cocoa powder. Mix on low speed until just combined and uniform in color. Gently spoon the chocolate batter over the peanut butter layer, then carefully spread it into an even layer with an offset spatula.

Place the foil-wrapped springform pan into a large roasting pan. Bring a pot or kettle of water to a boil. Carefully pour the hot water into the roasting pan until it comes about 1 inch up the sides of the springform pan.

Carefully transfer the roasting pan to the oven. Bake at 325°F (165°C) for 65-75 minutes. The cheesecake is done when the edges are set, but the center 2-3 inches still have a slight jiggle.

Turn off the oven and crack open the door. Let the cheesecake cool in the oven for 1 hour. This slow cooling process helps prevent cracks.

Remove the cheesecake from the water bath and take off the foil. Let it cool completely on a wire rack to room temperature. Once cool, cover loosely with plastic wrap and refrigerate for at least 6 hours, or preferably overnight.

Once the cheesecake is fully chilled, prepare the ganache. Place the chocolate chips in a heatproof bowl. Heat the heavy cream in a small saucepan or in the microwave until it just begins to simmer. Pour the hot cream over the chocolate and let it sit for 5 minutes.

Whisk the mixture until the chocolate is completely melted and the ganache is smooth. Let it cool for 10-15 minutes, until it's slightly thickened but still pourable.

Pour the ganache over the top of the chilled cheesecake and spread it to the edges. Immediately sprinkle with chopped mini peanut butter cups, if using. Return the cheesecake to the refrigerator for at least 30 minutes to set the ganache.

To serve, run a thin knife around the edge of the cheesecake before removing the springform ring. Slice with a large, sharp knife, cleaning the knife between each cut for clean slices.