Preheat oven to 350 degrees. Spray a 9 x 13 inch baking pan with non stick cooking spray.
In a large microwave-safe bowl, microwave butter until completely melted. Stir in sugar and vanilla.
Add eggs one at a time, hand-beating well with spoon after each addition.
Add cocoa and beat until well blended. Add flour, baking powder and salt; beat well.
Fold in Andes Mint chips.
Pour batter into prepared pan and bake for 30 - 35 minutes.
While brownies are baking, unwrap all of the Andes Mint candies. When brownies are finished, remove from oven and immediately place all of the unwrapped candies on top of the brownies. Let them sit for about 5 minutes (or until they get soft and melted) and then using the back of a large spoon, spread the melted chocolate around until the brownies are completely covered by melted chocolate.
Let brownies sit for about an hour or until they have cooled completely (you can speed up the cooling process by sticking them in the fridge).
Cut into squares and enjoy.