Ingredients
Method
Step-by-Step Baking Walkthrough
- Preheat oven to 350°F (175°C). Line an 8x8-inch metal baking pan with parchment paper, leaving an overhang on two opposite sides for easy lifting. Lightly brush parchment with butter or oil spray.
- In a large mixing bowl, whisk together the melted warm butter, vegetable oil, granulated sugar, and brown sugar until thoroughly combined. Add the two whole eggs, the extra egg yolk, and vanilla extract.
- Whisk the egg and sugar mixture vigorously by hand with a balloon whisk for a full 2 to 3 minutes. The batter will turn pale, thickened, glossy, and leave ribbons on the surface—this dissolved sugar reaction is the secret to getting a glossy, paper-thin crinkly crust!
- Sift in the cocoa powder, all-purpose flour, sea salt, and espresso powder. Switch to a rubber spatula and gently fold the ingredients together just until no dry pockets remain. Do not overmix, which would develop gluten and make brownies cakey instead of fudgy.
- Gently fold 1/2 cup of dark chocolate chips into the thick, glossy batter. Transfer batter into the prepared 8x8 baking pan, smoothing it evenly to the corners with an offset spatula.
- Scatter the remaining 1/4 cup chocolate chips across the surface. Bake at 350°F (175°C) for 24 to 28 minutes. A toothpick inserted into the center should emerge with moist, sticky crumbs attached, but not liquid batter. Do not overbake!
- Transfer pan to a wire rack. Sprinkle a light pinch of flaky sea salt over the top while warm. Allow brownies to cool completely in the pan for at least 1 hour so the fudgy structure sets. For razor-sharp bakery squares, chill in the refrigerator for 30 minutes before slicing into 9 squares.
