• Preheat your oven to 325°F. Wrap the outside of a 9-inch springform pan with tin foil, wrapping it at least three times to ensure no leaks.

Oreo Crust

• Crush the cookies (wafers and filling) in a food processor until fine crumbs. Alternatively, place them in a freezer bag and crush with a rolling pin.
• Mix the cookie crumbs with the melted butter. Press the mixture into the bottom of the springform pan, creating a slight lip around the edges.
• Bake in the preheated oven for 8 minutes. Remove from the oven but keep the oven on.

Cheesecake Filling

• Chop the chocolate into fine pieces and place in a heatproof bowl. Microwave in 30-second intervals at medium power, stirring between each interval until smooth. Set aside.
• In a large bowl, beat the cream cheese and sugar until smooth. Add the melted chocolate and mix well. Turn off the mixer and scrape down the sides and bottom of the bowl.
• Whisk together the cocoa and water in a small cup. Beat the dissolved cocoa and sour cream into the batter. Mix in the eggs one at a time, stopping as soon as the batter is smooth.

Baking and Cooling

• Place the springform pan (still wrapped in tin foil) in the middle of a large roasting pan. Pour the cheesecake filling over the crust and smooth the top.
• Pour hot water into the roasting pan until there's about 1/2 - 1 inch of water in the pan. Bake for 55-65 minutes, or until the top looks just set. It should still wobble in the middle when gently nudged.
• Remove from the oven and let the cheesecake cool in the roasting pan until the water reaches room temperature. Remove the springform pan from the roasting pan and continue cooling on a wire rack (do not unclamp the outer ring of the springform pan).
• Once the pan is at room temperature, cover it with foil and place it in the fridge to chill for at least 6 hours or overnight.

Topping & Serving

• Pit the cherries and slice them in half. Add the cherries, sugar, and lemon juice to a medium saucepan over low heat. Stir gently as the cherries soften and release their juices.
• Dissolve the cornstarch in the water, then add it to the cherries and stir until the mixture thickens. Remove from heat.
• Beat the whipping cream and powdered sugar until peaks form. Transfer the whipped cream to a piping bag (using a 1M Wilton tip if desired).
• Remove the cheesecake from the fridge. Trace around the outer edge with a sharp knife, then unclamp the outer ring of the pan.
• Pipe rosettes around the edges of the cheesecake and spoon the cherry topping in the middle. Optionally, add chocolate shavings over the whipped cream.
• Slice with a thin, sharp knife, ensuring you cut all the way through the crust.