Preheat the oven to 350°F. Grease an 8×8 pan. For easy removal of the brownies, place parchment paper on the bottom and 2 sides of the pan. Grease again and then set aside.
Using a double boiler method on medium heat, melt the butter. Then add in the chocolate and mix until glossy and smooth. Remove from heat and allow to cool for 10 minutes.
3/4 cups butter, 1 1/4 cups semi-sweet chocolate chips
In a large bowl, add eggs, egg yolk, vanilla, brown sugar, and white sugar. Whisk until pale and bubbly (2-3 minutes).
1/2 cup dark brown sugar, 1/2 cup white sugar, 2 eggs, 1 egg yolk, 1 tbsp vanilla
Add in the chocolate mixture and mix together gently using a spatula until well combined.
Add in the flour, cocoa powder, and salt. Fold until a brownie batter forms.
3/4 cup all-purpose flour, 1/3 cup unsweetened cocoa powder, 1/4 tsp salt
Pour the batter into the prepared baking dish, spread evenly, and top with a handful of chocolate chips and Andes mint chocolates.
20 Andes mints, 1/2 cup semi-sweet chocolate chips
Bake the brownies for 22-28 minutes. Mine took 28 minutes. The brownies are ready when a toothpick inserted comes out slightly fudgy. If the batter is wet, keep baking for an additional 5 minutes.
When ready, slightly open your oven door and allow the hot air to escape. If you just take them straight out of them oven, the brownies will drop. After 10 minutes, remove from the oven and allow to cool on your counter before slicing. You can speed up the cooling process by placing them in the fridge as well.
Enjoy!