Prep the pan and oven. Heat the oven to 325°F (163°C).
Line the bottom of a 9-inch springform pan with parchment and lightly grease the sides. Wrap the outside of the pan with a double layer of foil to keep water out during baking.
Make the cookie crumbs. In a bowl, mix almond flour, cocoa, powdered sweetener, and salt. Stir in melted butter and vanilla until it forms a damp, sandy mixture.
It should clump when squeezed.
Form the crust. Press about two-thirds of the crumb mixture firmly into the bottom of the pan. Use a flat-bottomed glass to pack it tight. If it seems dry, add 1–2 tablespoons melted butter and mix before pressing.
Par-bake the crust. Bake the crust for 8–10 minutes until set and slightly darker.
Let it cool while you make the filling. Keep the oven at 325°F (163°C).
Beat the cream cheese. In a large bowl, beat softened cream cheese on medium-low until smooth and lump-free, about 2 minutes. Scrape the bowl often to avoid clumps.
Add sweetener, salt, and vanilla. Mix in the powdered sweetener, salt, and vanilla until well combined and creamy.
Blend in sour cream. Add sour cream and beat just until smooth.
Avoid whipping too much air into the batter.
Add eggs one at a time. Mix in the eggs on low speed, one by one, scraping the bowl between each. Stop as soon as they’re incorporated for the silkiest texture.
Fold in cookie chunks. Gently fold in the remaining cookie crumbs so you get streaks and bits throughout the filling. Don’t overmix.
Prepare a water bath. Place the foil-wrapped springform in a large roasting pan.
Pour hot water into the pan until it reaches about halfway up the sides of the springform.
Fill and bake. Pour the cheesecake batter over the crust and smooth the top. Bake for 55–70 minutes, until the edges are set and the center still jiggles like Jell-O.
Cool gradually. Turn off the oven, crack the door, and let the cheesecake sit for 45–60 minutes. This slow cool helps prevent cracking.
Chill completely. Remove from the water bath, discard the foil, and cool to room temp.
Cover and chill at least 6 hours, preferably overnight.
Finish and serve. Run a thin knife around the edge, release the springform, and transfer to a platter. Add whipped cream and extra cookie crumbs if you like. Slice with a hot, clean knife for neat pieces.