Preheat oven to 350 and line 9X13 baking dish with parchment paper.
Over a double boiler melt the dark chocolate (first measure of chocolate) and butter together over low heat.
In mixing bowl (stand mixer will work) beat eggs, sugar and vanilla together. Once chocolate is melted and cooled a bit (so you don't immediately cook the eggs when it is added) add the chocolate and butter mixture to the eggs in the stand mixer and beat well.
Remove from the stand mixer and fold in flour and salt until just mixed. Fold in the chocolate chips. Then pour into the prepared pan.
Bake at 350 for about 25 minutes. Top will begin to form a bit of crust and crack a bit. Do not over cook as it will dry out the brownies. Allow to cool before slicing. Serve warm.