Preheat oven to 350 degrees F. Lightly spray a 9x13 baking pan then line with parchment paper, spraying it first helps the parchment paper to stick.
In a large mixing bowl or stand mixer beat together the butter, sugar, brown sugar and vanilla.
Once the mixtures have combined, add the eggs in one at a time, beating in between each addition.
In a small mixing bowl sift together the flour, cocoa powder, baking soda and salt.
Slowly mix in the dry ingredients to the butter mixture.
Coarsely chop 1 of the chocolate bars into chunks. Then with a wooden spoon or spatula mix in the one (1) bar of chocolate that is chopped or 1 cup of the chocolate chips.
Spread the batter into the 9x13 prepared pan.
Coarsely chop 1 the remaining chocolate bars into chunks, sprinkle over the brownie batter in the pan and gently press into the batter.
Bake for 30-35 minutes, until brownies begin to pull away from the side of the pan.