Preheat the oven to 350°F and prepare an 8-inch cake pan with parchment paper and light grease so the delicate cake releases cleanly after baking.
Melt the chocolate chips and butter together slowly until smooth and glossy, stirring carefully to prevent overheating or grainy texture.
Mix in sugar, cocoa powder, vanilla, salt, coffee, and espresso powder until fully combined and smooth throughout the batter.
Allow the chocolate mixture to cool slightly, then whisk in the eggs one at a time until the batter becomes shiny and slightly thickened.
Pour the batter into the prepared pan and bake for 28–32 minutes until the edges are set and the center still jiggles slightly.
Cool the cake in the pan before transferring to a rack, then garnish with cocoa powder, berries, whipped cream, or chocolate shavings before serving.