Preheat oven to 375°F. Grease an 8" round cake pan and set aside.
In a large microwave-safe bowl, melt the chocolate with the butter, working in 30 second intervals and stirring between each interval.
Add all ingredients into the melted chocolate and butter mixture, and stir until combined. Pour the batter into the prepared cake pan and bake for 30-32 minutes. Allow the cake to cool completely, then chill in refrigerator for about 2 hours before inverting onto a plate to serve.