Cheesecake:

Let 2 eggs, 3 bars (8 oz each) of full-fat cream cheese, and 1 cup (about 8 oz) of full-fat sour cream come to room temperature. Adjust oven rack to the lower-third position, and preheat your oven to 350 F (175 C), and begin boiling a large pot of water for the water bath.

Take 30 Oreo cookies. Twist apart the cookies and scrape out the filling into a bowl. Set the filling aside for now. Add the cookies into a food processor and pulse until it looks like fine crumbs. This should make about 2 cups of Oreo crumbs. Transfer Oreo crumbs into a medium-sized mixing bowl, add 2 tbsp of granulated sugar, and whisk these together. Then add 5 tbsp of unsalted butter that has been melted and 1 tsp of vanilla extract. Mix these together until they are well combined.

Take a 9" springform pan, and lightly butter the bottom and the sides. Transfer the Oreo crumb mixture into the springform pan and press the mixture into the bottom of the pan and about 1 inch up the sides. I like to use the bottom of a measuring cup to pack it in just tight enough so they stick together, but not too tight that the resulting crust is too hard. Set this crust aside in the freezer while preparing the cheesecake filling so the crumbs set.

In the bowl of your stand mixer, add in 2 1/2 bars (20 oz total) of room temperature cream cheese and 3/4 cup of granulated sugar. With the paddle attachment, mix these together on medium-high speed till it looks smooth. (Wrap the remaining cream cheese in its original wrapping and set it aside at room temperature for now)

Stop the mixer and add in 1 cup of full-fat sour cream, 2 tsp vanilla extract, 1 1/2 tbsp of all-purpose flour. Continue to beat on medium speed until everything is well combined.

One at a time, add in the 2 room temperature eggs, making sure that the previous egg is fully incorporated before adding the next one. Make sure to scrape down the bowl after the addition of each egg.

Place 6 Oreo cookies on the bottom of the prepared Oreo crust in the springform pan. Pour half of the cheesecake batter into the springform pan. Place another 6 Oreo cookies on top of the batter. Then pour the remaining half of the batter into the prepared crust and tap the pan on the counter a few times to bring all the air bubbles to the surface.

Place 2 large sheets of aluminum foil over a large roasting tray. I use an 11" x 15" roasting tray that's 2" high. You can use any size, as long as the springform pan fits inside it. Place the springform pan in the center of the foil, and fold up the foil so that it creates a high 2-layer wall of foil that is hugging the sides of the springform pan, and overshooting a bit in terms of height - about 1 inch or so higher than walls of springform pan. It's important that there are no holes or tears in the foil so water will not leak into the cheesecake. The 2 layers of foil will help to ensure this.

With the 9" springform pan in the center of the larger roasting tray and the wall of aluminum foil in place, place the roasting dish on the lower third rack in your preheated oven, with the roasting dish not pushed all the way in. Do not close the oven door yet. When the roasting dish is in the oven, pour boiling water into the roasting dish so that it goes up about one inch high, creating a water bath for the cheesecake. The springform pan with the cheesecake should be heavy enough to weigh it down, and it will not float in the water. Very carefully (so water doesn't slosh around) push the roasting dish further into the oven so it is centered, and close the oven door.

(Pouring the boiling water while the roasting dish is already in the oven will avoid having to carry the heavy dish with boiling water inside it).

Bake at 350 F (175 C) for 40 minutes, until it is almost done. The cheesecake should mostly hold together, but still have a lot of jiggle to it in the center. You don't want it to be completely firm at this stage.

Leaving the oven door closed, turn off the heat, and let it rest in the cooling oven for 1 hour.

After resting in the turned-off oven / water bath for 1 hour, remove the water bath from the oven, and carefully lift the cheesecake out of the water bath. Be very careful as water could still leak into the cheesecake at this point.

Let the cheesecake finish cooling to room temperature on a metal rack, uncovered.

While the cheesecake is cooling to room temperature, in the bowl of your stand mixer, add in the remaining 1/2 bar (4 oz) cream cheese, the Oreo filling (separated from cookies earlier, and 2 tsp of vanilla extract. With the paddle attachment, beat them together on medium speed until they are smooth.

Stop the mixer, and add in 1 cup of very cold heavy cream. Beat for about 1 minute, until the cream cheese and heavy cream are well combined. Scrape down the bowl and paddle attachment. Switch to the whisk attachment, and continue whipping on medium-high speed until the frosting holds stiff peaks.

Detach from stand mixer. Take 2 Oreo cookies and roughly chop them into small crumbly pieces. Fold the Oreo pieces/crumbs into the whipped cream mixture. Then using a mortar and pestle, crush 1 Oreo cookie into a very fine powder. Add this Oreo powder into the mixture, and fold it in until it makes a uniform Oreo Cookies & Cream mousse.

Place the room temperature cheesecake on a revolving cake stand. Carefully add the Oreo mousse on top of the room temperature cheesecake, smoothening the top as much as possible and making sure it goes all the way to the walls of the springform pan. Put it in the fridge to chill completely - minimum of 6 hours, preferably overnight.

Chocolate Ganache:

In a microwave-safe bowl, add in 1/2 cup of heavy cream and microwave for 1 minute, till the heavy cream is steaming. Add in 4 1/2 oz, which is about 3/4 of a cup, of dark or bittersweet chocolate chips, into the hot heavy cream. Let it stand for 1 minute, then gently whisk until the chocolate chips are completely melted and there are no lumps.

Cover with plastic wrap, then refrigerate for a minimum of 6 hours, preferably overnight together with the cheesecake.

The next day (or when the chocolate ganache and cheesecake are chilled), transfer the chocolate ganache mixture to the bowl of your stand mixer and add in 2 tbsp powdered sugar. Using the whisk attachment, beat it on medium-high speed, till it becomes fluffy and forms stiff peaks.

Decorating the Cheesecake:

Unlatch the springform pan and carefully lift off the sides, revealing the cheesecake. Place your cheesecake on a revolving cake stand. Take an offset spatula, and press it against the edges of the OREO Cookies & Cream mousse so that it's flush with the walls of the OREO cookie crust while rotating the revolving cake stand. Then flatten out the top surface in the same way so that everything is as smooth and even as possible.

Attach a coupler to your piping bag so we can switch to different tips easily. Start with a small round tip (we use a #3) attached to the coupler. Transfer the whipped chocolate ganache frosting into the piping bag. Create drizzles on top of your cake in whatever pattern you like. I like making overlapping circles of different sizes in a somewhat random pattern.

Switch to a large star tip (we use a #1M tip). Create rosettes of chocolate ganache around the top surface of the cake, right at the edge of the cake. Keep refrigerated until ready to serve. Enjoy!