Position oven rack in the lower third of the oven; preheat oven to 350°; butter and flour a 9 inch baking pan; set aside.
In a bowl, cream the butter and brown sugar using an electric mixer at medium speed; continue beating until pale brown and thick, about 5 minutes.
Beat in the molasses until smooth and uniform.
Then beat in the eggs one at a time, allowing the first to be thoroughly incorporated before adding the second; scrape down sides of bowl as needed.
With a wooden spoon or rubber spatula, stir in first the chocolate chips, then the flour mixture, just until incorporated—do not beat.
Spoon batter into pan, spreading it gently into the corners.
Bake for 20 minutes or until the top is light brown and pick comes out clean; set pan on a wire rack to cool for at least 30 minutes.
Cut the blondies into 16 squares while they are still in the pan; carefully remove them with an offset spatula.
Serve immediately, or let cool completely before covering with plastic wrap for storage at room temperature.