Preheat the oven to 350 degrees and line an 8x8-inch baking pan with parchment paper, creating "handles" that hang over the sides. Then spray with non-stick spray.
In a small microwaveable-safe bowl, melt the butter and allow it to cool on the counter for 5 minutes.
In a large bowl, whisk together the sugar, eggs, and egg yolk for 3 minutes (this step is crucial). Then whisk in the vegetable oil, vanilla extract, peppermint extract, and melted butter until combined.
Gently fold in the flour, cocoa powder, and salt just until combined. Scrape half of the brownie batter onto the bottom of the pan, spreading it out evenly. Place 14 chopped andes mints on top and cover them with the remaining brownie batter.
Bake for 30-35 minutes, or just until the edges are set and the middle of the brownies do not jiggle. You can also use a toothpick to check the center (the toothpick should come out clean with just a few crumbs). Cool on the counter for about 1 hour.
In a small microwaveable-safe bowl, melt the chocolate chips in 15 second intervals, stirring them each time, until completely melted.
Top the brownies with the rest of the chopped andes mints and then drizzle on the melted chocolate.
Once the brownies have completely cooled, remove them from the pan, slice, and serve. Keep any leftover brownies in an airtight container on the counter for up to 7 days.