Preheat the oven to 350 F and set a sheet of parchment paper on the bottom part of a 9” springform pan and clasp the top part over the parchment (it will just be on the bottom).
Mix the crumbs and melted butter together (you can do this straight in the pan if you like) and once they are well-blended press them on the bottom and up the sides of the pan. Use a measuring cup to press them down into a flat layer.
Bake the crust for 10 minutes. When it comes out it might look a bit soft or poofy in spots, use the measuring cup to press it down again. Once it’s cool, set it in the freezer.
Dark Chocolate Ganache
Set the chopped chocolate in a heatproof bowl. Warm the heavy cream in a small pot over medium heat. When it just begins to bubble on the sides and is hot to touch in the center, remove it from the heat and pour it over the chocolate. Let it set for a minute then stir it until you have a smooth ganache. Pour ganache onto the bottom of the crust and smooth it over into an even layer. Set in the fridge or freezer.
No-Bake Vanilla Cheesecake
Beat together the cream cheese, salt, vanilla and sugar until no lumps remain. Add the sour cream and beat to combine. In a separate bowl, whip the heavy cream until you have medium peaks (it will take at least 5 minutes, unless you are using a stand mixer, but be careful not to whip it too long). Fold the cream cheese mix with the whipped cream with a rubber spatula. Pour it on top of the ganache. Set in the fridge.
Serve and Store
To serve the cheesecake, first take an offset spatula and run it around the edges of the crust to loosen the pie from the pan. Open the clasp and carefully lift the cheesecake. It should be sturdy enough to lift the pie off the parchment and set it on a plate. Store it as is, uncovered, in the fridge, for up to 4 days. Serve cold.