1. Preheat oven to 375F. Butter and flour a 9- by 13-inch glass baking dish and set aside.
2. Stir butter into sugar in a large bowl until smooth, cool to room temperature.
Meanwhile, in another medium bowl, Whisk flour, baking soda, and salt together in a medium bowl; set aside. Beat eggs and vanilla into sugar mixture. Add flour mixture a bit at a time and mix until a smooth thick batter forms. Fold in chips, as desired.
3. Evenly spread batter into prepared dish. Bake until blondies are light brown around edges and a toothpick inserted in center, comes out clean, about 20 to 25 minutes.
Remove from oven; cool slightly. Invert onto a rack to release; cool completely. Cut into squares and serve.