Preheat oven to 350°. Grease a 9 x 13 baking pan and set aside.
Add the flour, cocoa powder, baking powder and salt to a medium mixing bowl. Whisk to combine. Set aside.
In a large mixing bowl, cream the butter, sugar and vanilla together until light and creamy.
Beat each egg into the mixture, one at a time. The batter will become very light and fluffy.
Add half of the dry ingredients and mix on medium speed until combined. Add the remaining dry ingredients and mix until well incorporated.
Fold the Andes chocolate mint chips into the batter.
Pour the brownie batter into the greased pan and bake for 30 to 35 minutes or until an insert a toothpick comes out clean
Cool completely on a wire rack before icing.