Preheat oven to 350 degrees F. Grease and line a 9x5 loaf pan with a parchment sling.
In the bowl of a food processor, combine 8 chocolate sandwich cookies, 1.5 tbsp melted butter, and a pinch kosher salt and process until uniformly crumbly and damp. Press into an even layer in the bottom of the prepared loaf pan (the bottom of a flat measuring cup can help tamp it down evenly). Bake for 10 minutes, or until the crust is fragrant and starting to look a bit dry. Set aside to cool slightly while you make the cheesecake.
In the microwave or over a double boiler, melt 2 oz semisweet chocolate, around 60% preferred. Set aside to cool slightly.
In a high-powered blender or bowl of a food processor, combine the rest of the ingredients: 1 cup cottage cheese, 1/4 cup Greek yogurt, 1 large egg, 3 tbsp granulated sugar, 2 tbsp natural or Dutch-process cocoa powder, 1.5 tbsp cornstarch and 1/2 tsp vanilla extract. Finally, add the slightly cooled semisweet chocolate. Blend until smooth.
Pour over the cookie crust and bake for 35-40 minutes, or until the cheesecake is puffed, set around the edges and jiggly rather than sloshy in the center. A few cracks on top are normal and expected--these will be slightly less noticeable as the cheesecake cools and deflates.Let cool for at least 30 minutes or up to an hour in the pan before removing. I like to refrigerate it overnight (or at least a few hours) before serving to let it settle, but you can also enjoy it right away.
Notes
I prefer 60% semisweet or bittersweet chocolate in this for a less sweet flavor, but you can use whatever you have on hand.You can use cottage cheese and Greek yogurt with any fat percentage. Full-fat will give the best flavor and texture, but I've also tried this with low-fat versions.This was adapted from my cottage cheese cheesecake.