Preheat oven to 325°F. Using a 9 inch springform pan, line it with parchment paper and spray with baking spray or butter.
Melt the Chocolate and Unsweetened Butter together in the microwave at 30 seconds intervals, until glossy and completely melted OR melt in the top of a double boiler over simmering heat until melted and glossy. Set aside and allow to cool.
Beat the Eggs, Sugar & Salt in a medium bowl with a mixer on medium, mixing until pale in color, about 5 minutes.
Now fold in the cooled Chocolate mixture into the beaten Eggs and mix until well combined.
Carefully pour batter into lined and greased 9 inch springform pan and bake in the 325°F pre-heated oven for 1 hour,15 mintues or until toothpick/cake tester inserted comes out clean.
Allow to cool in pan completely before removing the ring.
Once cooled, Dust with Cocoa Powder or Powdered Sugar, or garnish as desired.