Preheat oven to 350°F. Prepare 13 in. x 9 in. pan with vegetable pan spray.

In small bowl, combine flour and salt. In large microwave-safe bowl, microwave butter and chopped chocolate at half (50%) power for 60 seconds. Stir thoroughly. Continue to microwave and stir at 30 second intervals until smooth and completely melted. Stir in sugar, eggs and vanilla; mix well. Add flour mixture; stir until just combined. Stir in chips. Spread into prepared pan.

Bake 25-30 minutes or until toothpick inserted in center comes out almost clean. Cool brownies completely in pan on cooling grid.