Preheat the oven to 350 degrees (F). Grease and flour an 8 x 8-inch pan and line with one piece of parchment paper cut to fit the sides, but long enough to act as handles on two sides for removing the blondies.
Melt the butter and set aside.
Mix together the flour, baking powder, and salt and set aside.
Beat the eggs with the dark brown sugar until thick and lighter in color. Beat in the bourbon and vanilla.
With the mixer on low, alternate adding the flour mixture and butter. Give one quick mix to combine and pour half of it into the pan.
Sprinkle the chocolate chips in a single layer and pour the remaining batter over them, spreading it out over the top. If adding flaky salt, dust the top with a pinch or two.
Bake 20 minutes. (Do not bake longer or else they won't be chewy!)
Using the edge of the parchment paper as handles, lift out of the pan and cool on a baking rack. They can be eaten warm or cold.