Prep the pan. Heat your oven to 325°F (165°C).
Line the bottom of a 9-inch springform pan with parchment. Wrap the outside with two layers of foil to guard against leaks in the water bath.
Make the crust. Combine cookie crumbs, melted butter, sugar, and salt. Press firmly into the bottom and 1 inch up the sides of the pan.
Bake for 8–10 minutes, then set aside to cool slightly.
Melt the chocolate. Gently melt the bittersweet chocolate in a heatproof bowl over barely simmering water or in short microwave bursts. Stir until smooth and let it cool to lukewarm.
Beat the cream cheese and sugar. In a large bowl, beat the cream cheese with sugar until smooth and fluffy, about 2 minutes. Scrape the bowl.
Avoid whipping in too much air.
Add sour cream, espresso, vanilla, and salt. Mix until combined and silky. The mixture should be smooth with no lumps.
Blend in the eggs. Add eggs one at a time, mixing on low just until incorporated. Scrape the bowl after each.
Do not overmix.
Add the melted chocolate. Pour in the cooled chocolate and mix on low until fully blended and uniform. The batter will be thick and glossy.
Assemble the water bath. Pour the filling into the crust. Set the pan inside a larger roasting pan.
Pour hot water into the roasting pan until it comes halfway up the sides of the springform.
Bake gently. Bake at 325°F for 55–70 minutes. The edges should be set, and the center should have a slight wobble. If it ripples loosely, give it 5–10 more minutes.
Cool slowly. Turn off the oven, crack the door, and let the cheesecake rest inside for 1 hour.
Then remove the bath, unwrap the foil, and cool to room temperature.
Chill overnight. Cover and refrigerate at least 6 hours, preferably overnight. This sets the texture and deepens the flavor.
Make the ganache. Heat the cream until steaming. Whisk in espresso powder and salt.
Pour over the chopped chocolate, let sit 2 minutes, then whisk until smooth and glossy.
Glaze the cheesecake. Release the cheesecake from the pan and transfer to a platter. Pour the ganache over the top and nudge it to the edges for a smooth finish. Chill 20–30 minutes to set.
Serve. Slice with a hot, clean knife for neat edges.
Add whipped cream, chocolate curls, or a pinch of flaky salt if you like.