Lower the oven temperature to 325 degrees F.
In a large bowl or stand mixer, beat the softened cream cheese for 4 minutes, making sure to scrape the sides and bottom.
Add 1 and 3/4 cup sugar, 1/4 cup cocoa, 1 tablespoon vanilla, and 1/2 teaspoon salt. Beat for another 4 minutes, scraping sides and bottom.
Add 12 ounces of bittersweet chocolate to a medium bowl, breaking it up into pieces. Microwave in 30 second increments until it is mostly melted, stirring each time. Once the chocolate is mostly melted but has a few lumps, don't put it back in the microwave, just stir until the lumps are gone. Set the smooth melted chocolate aside to cool a bit.
Once the chocolate has cooled for a couple minutes, add it to the cream cheese mixture. Beat well, scraping sides and bottom.
Meanwhile, add the cream to a small pot on the stove. Heat over medium low heat until it is warm. You don't want it to boil.
While that is heating up, crack 10 egg yolks into a mixing bowl. (Save the egg whites for something else!)
Beat the egg yolks with a hand mixer for about 2 minutes, until they are pale.
Pour the heated cream through a fine mesh strainer into a large pourable glass measuring cup (or anything that pours).
While the beaters in the egg yolks are on, slowly add the warm cream. If you are not mixing while you do this, the eggs will curdle. Enlist help if you can. Don't try to take a photo during this step. I'm just watching out for you. I actually got my daughter to help me, so I skipped step 7 above and just had her hold the strainer over the bowl of eggs while I held the running mixer and pour in the hot cream (see photo.) Beat for 1 minute.
Once all of the hot cream has been incorporated with the egg yolks, pour the egg mixture into the cream cheese mixture and start beating right away. Make sure you scrape the sides and get out all the lumps. The batter will be pretty thin.
Transfer the foil-wrapped Oreo crust into a large high-sided skillet, or a roasting pan.
Pour the batter into the Oreo crust, forming an even layer on top.
Fill the skillet or roasting pan with hot water from the tap. You want the water to go at least halfway up the pan of the cheesecake.
Carefully transfer the water bath to the oven.
Bake at 325 for about 1 hour and 20-25 minutes. You will know it is done when it is mostly set in the center and doesn't jiggle too much when you shake it. (some movement is ok--it will continue to set as it cools. It just shouldn't be liquidy.) A toothpick inserted into the cheesecake 1 inch from the outer edge should come out with no batter on it.
Turn off the oven, but do not take the cheesecake out of the oven. Crack the door open and let the cheesecake come to room temperature inside the oven. (At least 1 hour, or up to 2 hours.)
When the cheesecake is room temperature, remove from the water bath, and remove the foil. Cover the cheesecake with plastic wrap and refrigerate for at least 3 hours or preferably overnight.