Heat oven to 350°F and spray a 13×9-inch baking pan with nonstick spray.
In a small bowl, whisk together flour and salt; set aside.
In a large bowl, combine butter and sugar and cream together until lighter in color and fluffy.
Add eggs, one-at-a-time. Beat well after each addition.
Add syrup and vanilla – beat well.
Sprinkle the flour/salt mixture over the chocolate mixture and mix just until no dry flour remains.
Pour into the prepared baking pan.
Bake 30 minutes at 350°F for 30 minutes (the brownie top will still appear wet). Transfer brownies to a wire rack to cool completely.