Preheat your oven to 325°F (163°C). Prepare a 9-inch springform pan by lightly greasing it or lining it with parchment paper.
Start with the crust: Combine almond flour, cocoa powder, and granular erythritol in a mixing bowl. Add the melted butter and mix until a crumbly dough forms.
Press the dough into the bottom of the prepared springform pan, creating an even layer. Bake for about 10 minutes, then remove from the oven and let cool.
For the filling, beat the softened cream cheese and powdered erythritol together in a large bowl until smooth and creamy.
Add the eggs one at a time, fully incorporating each before adding the next. Stir in the sour cream and vanilla extract.
Sift in the cocoa powder to avoid lumps and mix until well combined. Fold in the melted dark chocolate until the mixture is uniform.
Pour the filling over the cooled crust and smooth the top with a spatula.
Bake for 45 minutes, or until the edges are set but the center is still slightly jiggly.
Turn off the oven, crack the door open, and allow the cheesecake to cool inside for 1 hour. This helps prevent cracking.
Remove the cheesecake from the oven and let it cool to room temperature before transferring it to the refrigerator to chill for at least 4 hours, preferably overnight.
Once chilled, release the cheesecake from the springform pan, slice, and serve.