Rich, chewy brownie with chocolate chips on top.
Swapping white sugar for dark brown sugar alters the moisture content, driving the dense, butterscotch profile characteristic of proper blondies. Temperature management dictates the final texture. Incorporating boiling-hot butter directly into the egg will scramble it, so allow the melted butter and sugar emulsion to cool before adding the beaten egg. Overmixing the flour activates the gluten network, producing tough bars rather than tender ones. Fold the dry ingredients into the wet base using a rubber spatula just until no white streaks remain. Sifting the flour twice aerates the dense batter, ensuring an even rise alongside the quarter teaspoon of chemical leaveners. Spread the thick batter evenly into a greased 9x9-inch metal baking pan; glass dishes conduct heat differently and often cause uneven edges. Monitor the oven closely at the twenty-minute mark. Insert a wooden toothpick into the center; removing the pan when a few moist crumbs cling to the wood prevents dryness. Pair these rich, chocolate-topped squares with unsweetened cold brew coffee to balance the concentrated sugar content.