Step 1: Prepare the pan and oven

Set your oven to 325 F or 163 C. Line the base of a 9 inch springform pan with parchment, lock in the ring, and lightly grease the sides. Wrap the outside with two layers of wide, heavy duty foil to waterproof it for a water bath. Place a kettle of water on to heat.

Tip: A light greasing of the sidewalls lets the cake release and contract without tearing as it cools, which reduces surface cracks.

Step 2: Make the chocolate cookie crust

Pulse the cookies into fine crumbs or crush them in a bag with a rolling pin. Mix with melted butter and a pinch of salt until the texture feels like wet sand. Press firmly into the pan base and up the sides by 1 inch using a flat-bottomed glass. Bake 8 minutes, then cool while you build the filling.

Tip: A firm press-in prevents floating when the water bath steams and keeps slices neat.

Step 3: Melt and temper the chocolate

Place 225 g chopped dark chocolate in a heatproof bowl. Microwave in 20 second bursts, stirring often, until just melted and smooth. Let it cool to lukewarm. Warm the heavy cream slightly so it does not shock the chocolate when folded into the batter.

Tip: Aim for chocolate at 90 to 95 F. Too hot and it can seize the batter. Too cool and it streaks.

Step 4: Mix the cream cheese base

With a stand mixer on low or a hand mixer, beat the cream cheese until creamy and lump free, 60 to 90 seconds. Add sugar, cocoa, espresso powder, and salt. Mix on low just until combined, scraping the bowl once or twice. Blend in sour cream and vanilla. The mixture should be satin-smooth.

Tip: Keep the speed low. Air is the enemy of a smooth cheesecake. Low speed mixing limits bubbles that can expand and crack during baking.

Step 5: Add eggs the smart way

Lightly whisk the eggs in a measuring cup to break them up. Stream them into the batter in three additions on low speed, fully incorporating each one before the next. Stop the mixer as soon as no streaks remain.

Tip: Overbeating at this stage creates volume that collapses in the oven. Your batter should look pourable, not fluffy.

Step 6: Fold in chocolate and cream

Whisk the lukewarm melted chocolate with the warmed heavy cream until glossy, then fold this mixture into the batter with a flexible spatula. Work gently from the center out. Pour into the crust and tap the pan twice on the counter to bring up any bubbles. Pop visible surface bubbles with a toothpick.

Step 7: Bake in a moderated steam environment

Set the foil-wrapped pan into a large roasting pan. Pour hot water into the roaster to reach halfway up the sides of the springform pan. Bake 55 to 65 minutes. The edges will be set about 2 inches in, with a center that jiggles like set gelatin, not like liquid.

Alternative: If you are wary of leaks, place a separate pan of hot water on a lower rack instead of a full water bath. You will lose a touch of humidity but still gain gentler heat and fewer cracks.

Step 8: Cool gradually, then chill fully

Turn off the oven, crack the door, and let the cheesecake rest for 60 minutes in the gentle heat. Move to a rack and run a thin knife around the edge. Cool to room temperature, then cover and chill at least 6 hours or overnight.

Tip: That clean edge cut is not cosmetic. It prevents the sides from sticking and tearing as the cake contracts.

Step 9: Finish with ganache

Heat 120 ml cream to steaming. Pour over 115 g chopped chocolate with optional corn syrup and let sit 2 minutes. Stir until glossy. Cool to a pourable consistency and spread over the chilled cake. Return to the fridge for 20 minutes to set.

Step 10: Slice like a pro

Dip a long, sharp knife in hot water, wipe dry, and slice with firm downward strokes. Rinse and wipe between cuts. Serve cold or allow 15 minutes at room temperature for a softer bite.