1. Preheat the oven to 375 degrees. Lightly grease a metal 8″ round cake pan. Trace and cut a piece of parchment to fit the bottom. Lay it in the bottom of the pan and spray with nonstick spray.
2. Cake: Put the chocolate and butter in a microwave-safe bowl, and heat until the butter is melted and the chips are soft. Heat 30 seconds at a time and stir after each time. Transfer the melted chocolate and butter mixture to a mixing bowl.
3. Stir in the sugar, salt, coffee, and vanilla. Mix until just combined. (You can use a mixer on low or a bowl and wooden spoon. Add the eggs one at a time, mixing after each one. Add the cocoa powder, and mix just to combine.
4. Pour the batter into the prepared pan. Bake the cake for 22 minutes. The top should look like it has formed a thin crust layer on top.
5. Remove it from the oven and cool it in the pan for 5 minutes. Loosen the edges of the pan with a table knife and turn it out onto a serving plate. The top will now be on the bottom. Allow the cake to cool completely before glazing.
6. Glaze: Place the chocolate in a heatproof bowl. Heat the cream in a saucepan over low heat until it’s just starting to simmer.
7. Pour the cream over the chocolate chips and let rest for 2-3 minutes. Start stirring slowly and once starting to melt, then stir faster. If any bits of chocolate remain, reheat briefly in the microwave, then stir until smooth.
8. Spoon the glaze over the cooled cake, spreading it so it drips over the sides a bit. Allow the glaze to set for a few hours before serving the cake.

Original Recipe From King Arthur Flour