Whisk together dry ingredients and set aside. Add wet ingredients to a mixing bowl and mix with a beater until well combined. Add dry ingredients to wet and stir just until combined.
Pour batter into prepared pan. Shake pan to evenly distribute batter. Bake for 40 minutes, or until a cake tester comes out clean. Allow to cool in pan for 15 minutes and then invert onto cooling rack.
Place all ingredients in a small saucepan over medium-low heat, stirring constantly until chocolate has melted and all ingredients are incorporated. Remove from heat and allow to cool slightly.
Place cake on plate or cake stand and slowly pour the sauce over top of the cake.