Preheat oven to 350°F and grease and line a 9x9 inch pan with parchment paper.
In a medium bowl, melt the butter, chocolate chips and ½ cup of Andes mints. While microwaving, stir every 30 seconds until the mixture is smooth. Let it cool slightly.
In a large bowl, whisk together the eggs, granulated sugar and brown sugar for about 1 minute. Then, gradually stir in the slightly cooled chocolate mixture. Mix in the oil.
In a separate bowl, whisk together the flour, cocoa powder, baking powder and salt. Then, mix them into the large bowl of wet ingredients until almost all of the flour streaks disappear.
Gently fold 1 cup of chopped Andes mints into the brownie batter and then spread the batter evenly into the prepared pan. Sprinkle the top with finely chopped mints.
Bake the brownies until the center is just very slightly jiggly (start checking around 35-40 minutes, it can take up to ~50 minutes, a toothpick inserted into the center should come out slightly gooey/crumbly).Let the brownies cool in the pan until they're firm enough to remove by pulling up on the parchment paper. Cool completely before cutting into 16 squares with a warm chef's knife.
Notes
Andes Mints: I use about 50-60 total Andes mints for this recipe. You can also buy Andes Baking Chips to use instead.Storage: Store leftovers in an airtight container for up to 1 week or in the freezer for up to 1 month.