Set out butter and eggs to bring them to room temperature. In a double boiler or small saucepan with a large heatproof bowl, melt chocolate and 2 tbsp of butter until melted stirring frequently. Once melted, remove from heat and set aside.
In a medium bowl whisk flour, salt, and cocoa powder and set aside. In a mixer blend 1 stick of unsalted butter and sugars, add vanilla and eggs one at a time. Nex, add slightly cooled melted chocolate and blend well. Add remaining flour mixture and mix until blended well, not too much…do not over beat. Place batter in a greased 9″x12″ pan. Bake at 350 degrees for about 25 minutes.