Ingredients:
- 1 cup (2 sticks) unsalted butter
- 6 oz bittersweet or semisweet chocolate, chopped
- 1 cup granulated sugar
- 1/2 cup light brown sugar, packed
- 3 large eggs, room temperature
- 1 teaspoon vanilla extract
- 3/4 cup all-purpose flour, spooned and leveled
- 1/4 cup unsweetened cocoa powder (Dutch-process preferred)
- 1/2 teaspoon fine sea salt
- 1/2 cup chocolate chips or chunks (optional mix-in)
Instructions:
- Preheat oven to 350°F (175°C). Line an 8x8 inch square baking pan with parchment paper, leaving an overhang on two sides to create a sling.
- Melt the butter in a light-coloured, heavy-bottomed saucepan over medium heat. Continue cooking, swirling occasionally, until the milk solids turn deep golden brown and the butter smells nutty. Immediately pour into a heatproof bowl to stop the cooking process.
- Add the chopped bittersweet chocolate to the warm brown butter. Let stand for 2 minutes, then whisk until the mixture is completely smooth and glossy. Set aside to cool slightly (it should still be warm, but not hot).
- In a separate large bowl, combine the granulated sugar, brown sugar, and eggs. Using an electric mixer, beat on medium-high speed for 5–7 minutes until the mixture is pale yellow, thick, and has significantly increased in volume. Whisk in the vanilla extract.
- Gently whisk the slightly cooled brown butter/chocolate mixture into the egg/sugar mixture until just combined. Do not overmix.
- Sift the flour, cocoa powder, and salt over the batter. Gently fold them in using a rubber spatula until just combined. Fold in optional chocolate chunks now.
- Transfer the batter to the prepared pan, spreading it evenly. Bake for 30 to 35 minutes. The edges should look set, but the centre should still look slightly soft.
- Check doneness: A toothpick inserted near the centre should come out with moist, fudgy crumbs attached, not wet batter. Let the brownies cool completely in the pan on a wire rack for at least 2 hours before lifting by the parchment sling and slicing.