Preheat oven to 375°F. Mist a 12-cup muffin tin with nonstick cooking spray or line with paper muffin cups. In a small bowl, mix flour, baking powder and salt; stir with a fork to combine.
Melt butter in a medium saucepan over low heat. Remove from heat and stir in brown sugar. Let cool slightly, then stir in egg and vanilla until smooth. Stir in flour mixture, then chocolate chips and nuts, if using.
Portion out a little less than 1/4 cup batter into each muffin cup and smooth tops with a small spatula. Bake until just set, 15 to 17 minutes. Let blondies cool completely on a wire rack before removing from pan.
One of the better chocolate chip cookies I've had; so easy & fewer dishes to wash. I made a few changes for personal taste: I used 1/2 brown sugar & 1/2 granulated sugar. I don't like nuts, so I left them out & added an extra 1/4 c of chocolate chips. A couple of them caved in, but no harm done. I highly recommend using foil baking cups (without the paper liner) for easy removal.
Really guiltfully delicious....I say guilty because it calls for a great amount of sugar for a small batch...but it's really worth it for the day you need to just have something really good. I used the cupcake liners. I used dark pan and it took me an extra 3 minutes to bake.