Preparation Steps

• Line a 9-inch square metal baking pan with a parchment sling (overhang on two sides) and lightly coat with nonstick spray. Preheat the oven to 325°F (163°C).
• Chop the dark chocolate and melt it gently: set the bowl over barely simmering water or microwave at 50% power in 30-second bursts, stirring until smooth. Set aside to cool until just warm to the touch.
• For the crust, pulse the Oreo cookies to fine crumbs. Stir in the melted butter and sea salt until evenly moistened, then press firmly into the prepared pan (use a flat-bottom cup to compact).
• Par-bake the crust for 8 minutes, then place the pan on a rack to cool slightly while you prepare the filling. Keep the oven at 325°F.
• In a large bowl, beat the cream cheese on medium speed just until creamy, about 45–60 seconds. Add the sugar, cocoa powder, and espresso powder and mix on low until smooth, scraping the bowl and paddle as needed.
• Mix in the sour cream and vanilla until fully blended and silky.
• Add the eggs one at a time on low speed, mixing just until incorporated after each addition to avoid adding excess air.
• With the mixer on low, slowly stream in the cooled melted chocolate; finish by stirring with a spatula to ensure no streaks remain. Tap the bowl a few times to release any large bubbles.
• Pour the batter over the warm crust and smooth the top. Tap the pan twice on the counter.
• Bake for 22–25 minutes, until the edges look set and the center jiggles slightly like gelatin when nudged. Turn off the oven, crack the door open, and let the pan rest inside for 5 minutes before transferring to a rack.
• Cool to room temperature, then refrigerate until fully set, at least 3 hours (overnight for easiest slicing).
• For the whipped cream, chill a mixing bowl and whisk for 10 minutes. Whip the cold cream on medium-high to soft peaks, then add powdered sugar and vanilla; continue whipping to medium-stiff peaks.
• Lift the chilled slab from the pan using the parchment. Cut into 16 bars with a hot, dry knife. Dollop or pipe whipped cream onto each bar and serve.