Preheat to 350°F. then line an 8x8-inch metal pan with parchment and set aside.
In a heatproof bowl, combine butter, chopped chocolate, and oil. Melt gently (microwave in 30 sec bursts or over a double boiler), then stir in cocoa powder and the espresso powder until smooth. Let it cool slightly.
½ cup unsalted butter, 3 tbsp neutral oil, 4 oz 70% dark chocolate, chopped, 2/3 cup Dutch process cocoa powder, 1 tsp instant espresso powder
In a large bowl, beat eggs, yolk, granulated sugar, powdered sugar, and vanilla on high speed for 3-6 minutes until thick, pale, and ribbon-y. This is where that shiny crackle top is born!
2 large eggs, 1 egg yolk, 1 cup granulated sugar, ½ cup powdered sugar, 1½ tsp vanilla extract
With the mixer on low, slowly pour in the slightly cooled chocolate-butter mixture.
Sift the dry ingredients into the brownie batter mixture. Gently fold into the batter with a spatula. Mix in the Andes mint chocolates and chocolate chips leaving some aside to top the brownies with.
½ cup all-purpose flour, 1 tbsp cornstarch, ½ tsp kosher salt, 28 Andes Mint Chocolate, 1/2 cup chocolate chips
Pour the batter into the prepared pan, smooth the top, and tap the pan once on the counter. Top with more Andes Mint Chocolates and some chocolate chips then bake 23-25 minutes, or until a toothpick comes out with moist crumbs
Let cool in pan for a little bit before adding the toppings.