1. Preheat oven to 350°F and lightly grease an 8-inch round cake pan with cooking spray. Line the bottom with parchment and spray again.

2. Combine chocolate chips and butter in a large bowl. Microwave in 30-second bursts, stirring between each, until just melted and smooth. Let cool to room temperature.

3. Whisk sugar, espresso powder, salt, and vanilla into the cooled chocolate mixture until combined.

4. Add all eggs and the extra yolk at once. Whisk vigorously until the batter becomes smooth and glossy, about 30 seconds.

5. Sift cocoa powder over the batter and whisk gently until just combined.

6. Beat chilled heavy cream to medium peaks using an electric mixer. Stop when soft peaks form and hold their shape but still droop slightly.

7. Gently fold whipped cream into chocolate mixture with a rubber spatula, using broad strokes to keep the airiness.

8. Pour batter into prepared pan and bake 25-30 minutes until edges are set, center jiggles slightly, and internal temp reaches 200°F.

9. Let cake cool in the pan on a wire rack for 10 minutes, then loosen edges with an offset spatula. Cool completely, cover, and refrigerate at least 6 hours or overnight.

10. Use a hot, clean knife to cut slices. Run knife under hot water and wipe dry between each cut. Dust with powdered sugar and top with fresh berries.