1. Preheat the oven to 325°F (163°C). Add the butter to a small saucepan over medium heat and cook, swirling occasionally, until the milk solids turn golden brown and the butter smells nutty and aromatic. Remove from the heat.
2. While the butter is still hot, whisk in the dulce de leche. It may resist incorporating at first, but continue whisking until mostly smooth. Add the 8 oz (227g) of finely chopped chocolate and whisk until completely melted, smooth, and glossy. Set aside to cool slightly.
3. In a separate large bowl, whisk together the egg, egg yolk, vanilla extract, vegetable oil, baking soda, and salt until smooth and homogeneous. Slowly whisk in the warm chocolate mixture until fully incorporated.
4. Add the powdered sugar and cocoa powder and whisk until smooth. Add the flour and stir with a spatula just until no dry streaks remain. Fold in the roughly chopped chocolate just until evenly distributed, being careful not to overmix.
5. Lightly grease an 8” (20cm) baking pan with nonstick cooking spray. Cut a sheet of parchment paper slightly narrower than the pan but long enough to cover the bottom and two opposite sides, leaving a few inches of overhang on each side. Press the parchment into the greased pan. The overhanging parchment will act as handles for lifting the brownies from the pan after baking.
6. Transfer the batter to the prepared pan and spread it into an even layer, making sure to work the batter into the corners. Bake for 20–25 minutes, or until the edges are set and the center is still slightly soft. A toothpick inserted into the center should come out with a few moist crumbs attached, but no wet batter.
7. Let the brownies cool completely in the pan. Using the parchment sling, lift them from the pan and transfer them to a cutting board. Slice into 9 even squares, serve, and enjoy!

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