Preheat oven to 350 degrees F. Grease a 9x13-inch pan with cooking spray or line with parchment paper.
Mix together the melted butter and brown sugar. Add the eggs and vanilla and mix.
Add the flour, baking powder, baking soda and salt and mix just until combined.
Stir in the baking chips.
Bake for 24-28 minutes, or until a toothpick inserted in the center comes out clean. Allow to cool for about 20 minutes before cutting.
Store triple chip blondies in an airtight container at room temperature for 3-4 days. I think these blondies taste best the day they are made, but if you want to make them ahead of time I suggest freezing them! To freeze: Allow blondies to cool completely. Cut them and store them in a freezer safe container for up to 3 months.