Preheat oven to 375 degrees and lightly greased 8 or 9-inch round cake pan. Line the bottom with parchment paper.
Place chocolate chips and butter into a microwave safe mixing bowl. Microwave for 30 seconds at a time, stirring in between, until everything is melted and smooth.
Pour in sugar, cocoa powder, eggs, and vanilla extract. Use a hand mixer to beat together until just combined. Do not over mix. Scrape the sides and bottom of the bowl to ensure everything is mixed in.
Pour into the prepared cake pan. Bake 25 minutes in the preheated oven.
Let cool in the pan for 5 minutes. Run a knife around the edges to loosen, and flip the cake onto a serving platter or cake stand. Let cool completely.
Make the ganache by placing chocolate chips into a mixing bowl. Heat heavy cream in the microwave until simmering, about 45 seconds.
Pour hot cream over chocolate chips. Let stand 2 minutes, then stir until smooth.
Spread ganache over the top of the cake. Let cool before slicing and serving.