Step 1: Make the Crust

1. Preheat the Oven: Preheat your oven to 325°F (163°C). Line an 8×8-inch baking pan with parchment paper, leaving an overhang on the sides for easy removal.
2. Prepare the Cookie Crumbs: Crush the chocolate sandwich cookies in a food processor until finely ground. Alternatively, place them in a zip-top bag and crush them with a rolling pin.
3. Mix the Crust Ingredients: In a medium bowl, combine the cookie crumbs, melted butter, and sugar. Stir until the crumbs are evenly coated.
4. Press the Crust: Press the mixture firmly and evenly into the bottom of the prepared pan. Use the back of a measuring cup to ensure the crust is compact. Bake for 8–10 minutes, then let it cool slightly while you prepare the filling.

Step 2: Prepare the Cheesecake Filling

5. Beat the Cream Cheese: In a large mixing bowl, beat the softened cream cheese and sugar with an electric mixer on medium speed until smooth and creamy, about 2–3 minutes.
6. Add the Eggs: Beat in the eggs one at a time, mixing well after each addition. Scrape down the sides of the bowl as needed.
7. Mix in Sour Cream and Vanilla: Add the sour cream (or Greek yogurt) and vanilla extract, and mix until combined.
8. Add the Melted Chocolate: Pour in the melted and slightly cooled chocolate, and mix until fully incorporated. Be careful not to overmix to avoid adding too much air to the batter.

Step 3: Assemble and Bake

9. Pour the Filling: Spread the chocolate cheesecake filling evenly over the cooled crust. Smooth the top with a spatula.
10. Bake: Bake the cheesecake bars in the preheated oven for 35–40 minutes, or until the edges are set and the center is slightly jiggly. Avoid overbaking to prevent cracks.
11. Cool: Remove the bars from the oven and allow them to cool completely at room temperature for about 1 hour.

Step 4: Prepare the Ganache Topping

12. Heat the Cream: In a small saucepan, heat the heavy cream over medium heat until it begins to simmer (do not let it boil).
13. Melt the Chocolate: Place the chocolate chips in a heatproof bowl. Pour the hot cream over the chocolate and let it sit for 2–3 minutes, then stir until smooth and glossy. Add butter for extra shine, if desired.
14. Spread the Ganache: Once the cheesecake has cooled, pour the ganache over the top. Use a spatula to spread it evenly.

Step 5: Chill and Serve

15. Chill: Refrigerate the bars for at least 3 hours, or until fully set. For best results, chill overnight.
16. Slice: Use the parchment paper overhang to lift the bars out of the pan. Slice into 16 squares using a sharp knife, wiping the blade clean between cuts for neat edges.
17. Garnish: Decorate with chocolate shavings, whipped cream, fresh berries, or sprinkles as desired. Serve chilled.