Preheat the oven to 350 degrees F. Butter a 9-inch pie plate. (An 8×8-inch square pan may also be used. If the pan is dark-coated metal, reduce the oven temperature to 325 degrees.)
In a medium bowl, mix together the oil (or melted butter) and sugar until well blended. Beat in the eggs and balsamic (or vanilla).
In a separate bowl, combine flour, cocoa, baking powder, and salt. Gradually stir into the egg mixture until well blended. Spread the batter evenly into the prepared pan, and evenly distribute the chocolate chunks over the top.
Bake for about 18 minutes, or until the brownie begins to pull away from edges of pan. This is how long it takes in my oven to reach the point where the brownies are just cooked through yet still very moist. The brownies will still appear the slightest bit jiggly in the middle. All ovens vary, so check a few minutes early and know that it might take a few minutes longer than this.
Allow to cool, then cut and enjoy! I like to store the cooled brownies in the refrigerator, covered with plastic wrap. You may store at room temperature, if preferred.
