Preheat oven to 350 degrees F. Lightly spray pan with nonstick cooking spray.
Place the unsweetened chocolate and butter in a bowl over a pot of lightly simmering water. The water should not touch the bottom of the bowl. Stir frequently until chocolate and butter are completely melted and remove bowl from the pot.
Stir in the sugar. Then stir in the eggs and vanilla. Follow with the flour and salt, mixing just until combined. Stir in the chocolate chips. Spread the batter into the prepared pan.
Bake for about 35 to 40 minutes or until a toothpick inserted in the brownie comes out with moist crumbs.