Preheat oven to 350 degrees F. Spray a 9X13 baking pan with a nonstick cooking spray or parchment paper.
Beat together the butter, brown sugar and granulated sugar together in a large mixing bowl. Add in the eggs and vanilla extract. Mix until well combined.
In a separate bowl, stir together the four, cornstarch, baking powder and salt.
Then gradually stir in the flour mixture into the butter mixture by hand until just combined. Be careful not to over mix.
Then gently stir in the butterscotch chips.
Spread the batter into the baking pan and bake for 25-30 minutes until a toothpick inserted into the center comes out clean.
Allow the brownies to cool completely in the pan and then cut, serve and enjoy!
Notes
Store the leftovers in an air tight container for up to 5-7 days.