Begin by preheating oven to 350 degrees F. Line a square pan (8x8) with parchment paper with an overhang and set aside.
Add melted butter and brown sugar to a medium sized mixing bowl. Mix thoroughly.
Next, add egg and vanilla and mix some more.
In a separate bowl, sift together all dry ingredients: baking powder, baking soda, salt and flour.
Add dry ingredients to the butter and sugar mixture and mix until batter forms.
Add both chocolate chips and fold it into the batter.
Evenly pour the batter into the lined pan. Bake for 18 to 20 minutes or until the blondies pass the toothpick test (ie.: insert a toothpick into the center of the blondies, and if it comes out clean, then it is ready).