• Preheat the oven to 350F (180C) degrees.
• Wrap the outside of a 9-inch (23 cm) springform pan with aluminum foil at least 4 times so that the bottom and sides are covered, and that all seams are covered as well.

Oreo Crust

• Place the cookies (wafers and filling) in a food processor and blitz until the cookies are fine crumbs. Or place the cookies in a freezer bag and crush with a rolling pin.
• Mix the crushed cookies with the melted butter.
• Press the mixture into the bottom of the prepared pan and slightly up the sides (about 1/4 inch) so that there's a slight lip around the edges.
• Bake in the preheated oven for 10 minutes. Then remove from the oven (keep the oven turned on).

Cheesecake Filling

• Beat the cream cheese and sugar until soft. Turn off the mixer and scrape down the sides and bottom of the bowl as necessary.
• Beat in the cocoa powder and sour cream. (If the cocoa is lumpy, be sure to sift it first). Scrape down the bowl as needed.
• With the mixer on low speed, carefully mix in the buttermilk, vanilla extract, vinegar and food coloring.
• In a small bowl, whisk the eggs and egg yolks. Then carefully beat the eggs into the batter about 1/3 at a time until just incorporated.

Baking and Cooling the Cheesecake

• Place the crust (with the pan still wrapped in aluminum foil) in the middle of a large roasting pan.
• Pour the cheesecake batter over the crust and smooth the top.
• Pour boiling water into the roasting pan so that there's about 1/2-1 inch of water (1.5 to 2.5 cm) in the roasting pan.
• Place the roasting pan (with the cheesecake inside) in the oven (still at 350F degrees from baking the crust) and bake for 60-70 minutes. When the cheesecake is done baking, it should look just set on the top, except perhaps in the very middle. If you give the pan a nudge, it should wobble in the middle like Jello or pudding. If it wobbles like a liquid, then it's not done baking yet. I recommend checking around 50 minutes, just in case.
• Remove the roasting pan from the oven and allow the cheesecake to cool fully while still in roasting pan.
• Once the cheesecake has fully cooled, remove the cheesecake from the roasting pan. Cover the pan, and place in the fridge to chill for at least 6 hours or overnight. Do not unclamp the springform pan.

Cream Cheese Topping

• Beat the butter until soft, then mix in the cream cheese.
• Add in the salt, and with the mixer on low speed beat in the powdered sugar about 1/2 cup at a time until the desired sweetness is reached.
• Top the cheesecake with the cream cheese frosting, leaving a small perimeter around the edges. Return back to the fridge until ready to serve. Note - if you take the cheesecake out of the fridge and there is condensation on top, dab with a paper towel to remove.
• When ready to serve, unclamp the outer ring of the springform pan. Slice with a sharp knife (such as a paring knife - not a table knife), ensuring that you slice all the way through the crust.