Preheat your oven to 350°F. Line a 9x13 inch baking pan with parchment paper, allowing some overhang on the sides for easy removal later. This setup ensures even heat distribution and makes it simple to lift the cooled brownies out of the pan.

In a medium bowl, whisk together the cocoa powder and espresso powder. Pour in the 2/3 cup of boiling water and stir until completely smooth—the hot water blooms the cocoa and deepens the chocolate flavor. Add 1/3 cup of the chocolate chips and let them sit for 30 seconds, then stir until fully melted and glossy. I like to use Ghirardelli cocoa for its rich, deep color and Guittard chocolate for the perfect balance of sweetness and cocoa intensity.

Stir the melted butter and oil into the chocolate mixture from Step 2 until fully combined. In a separate small bowl, whisk together the room-temperature eggs, egg yolks, and vanilla extract until light and slightly frothy—this creates airiness in the batter. Slowly pour the egg mixture into the chocolate base while stirring constantly to temper the eggs gently and avoid scrambling them. The combination of whole eggs and yolks creates that signature fudgy texture.

Stir the sugar into the chocolate-egg mixture from Step 3 until completely incorporated and smooth. In a small bowl, whisk together the flour, salt, and baking powder. Add the dry mixture to the wet ingredients and fold gently with a rubber spatula until just combined—do not overmix, as this keeps the brownies tender and fudgy rather than cake-like. Fold in the remaining 1 cup of chocolate chips for pockets of melted chocolate throughout.

Pour the batter into the prepared pan from Step 1 and spread it into an even layer. Bake for 50-60 minutes at 350°F—I find the brownies are done when the edges look set and slightly cracked, but the center still has a slight jiggle when you gently shake the pan. A toothpick inserted in the center should have some moist crumbs clinging to it, not come out clean. Overbaking is the enemy of fudgy brownies, so err on the side of underdone.

Remove the brownies from the oven and let them cool completely in the pan at room temperature for at least 2 hours—this resting time allows the structure to set properly and makes them easier to cut without crumbling. For even cleaner cuts, you can refrigerate them for an additional 30 minutes before slicing. Use the parchment paper overhang to lift the entire block out of the pan, then cut into squares with a sharp knife, wiping the blade between cuts.