Preheat oven to 350F. Coat an 8" round cake pan with cooking spray then place a round piece of parchment paper in the bottom. Set aside. 

In a medium sauce pan over low heat, add the butter and chocolate chips. Stir continuously until melted and smooth. 

Sift in the sugar and espresso powder, whisking until combined. Whisk in the vanilla extract. Add the eggs one at a time, whisking between each addition. Once smooth, sift in the cocoa powder and whisk until combined. 

Pour batter evenly into prepared pan and bake for 20 – 25 minutes, until a thin crust forms on top of the cake. Let cool in pan for 5 minutes then transfer to cooling rack. 

To make the ganache, place chocolate in a medium size heat-proof bowl and set aside. Heat heavy whipping cream in a small sauce pan over low heat just until it starts to simmer. Pour over the chocolate and let sit for 5 minutes, then whisk until smooth. Let it cool slightly then pour over the cooled cake. Dust with cocoa powder if desired. Enjoy!