These fudgy sheet pan brownies have rich chocolate flavor, chewy edges, and classic crackly tops. They’re easy to make and yield plenty of brownies for sharing.
Preheat the oven to 350°F (175°C). Line a 10x15-inch jelly roll pan with parchment paper.
Whisk together the warm butter, oil, sugar, and brown sugar until glossy and combined.
Whisk in the eggs one at a time, whisking well after each addition, until the mixture is smooth, glossy, and slightly thickened.
Whisk in the vanilla and espresso powder (if using).
Add the cocoa powder and salt, whisking just until combined.
Fold in the flour just until a few small streaks remain. Add the chopped chocolate and fold just until combined.
Reserve a handful of chocolate for topping the batter before baking if you like.
Spread the batter evenly in the pan. If you reserved any chocolate pieces, sprinkle them over the top now.
Bake for 24 to 30 minutes, or until the edges are set and a toothpick inserted into the center comes out with a few moist crumbs.
Cool in the pan on a wire rack for 10 to 15 minutes. Sprinkle lightly with flaky salt, if using, then cool completely before cutting into squares.
Notes
Pan size: Use a 10×15-inch rimmed jelly roll pan for the intended thickness and texture. A larger 13×18-inch half sheet pan will produce much thinner brownies and is not recommended.
Chocolate: Chopped chocolate works best for creating melty pockets throughout the brownies, but you can use chocolate chips if that's what you have on hand.
Doneness: For fudgy brownies, remove them from the oven when a pick inserted into the center comes out with a few moist crumbs. Avoid baking until the pick is completely clean.
For clean slices: Cool the brownies completely before cutting. Lift them from the pan using the parchment, then slice with a large sharp knife, wiping the blade between cuts as needed.
Storage: Store the brownies in an airtight container at room temperature for up to 4 days. For longer storage, freeze them for up to 3 months and thaw at room temperature.