01 - Preheat your oven to 350°F. Line a 9x13-inch baking pan with parchment paper, ensuring an overhang on the sides for easy removal of the finished brownies. Set aside.
02 - In a microwave-safe bowl, combine the 1 cup unsalted butter and 8 oz bittersweet chocolate. Melt in 30-second intervals, stirring after each until smooth and fully melted. Allow the mixture to cool slightly.
03 - To the cooled chocolate mixture, whisk in the 1 1/2 cups granulated sugar and 1/2 cup packed light brown sugar until thoroughly combined and smooth.
04 - Add the 4 large eggs one at a time, whisking vigorously after each addition until fully incorporated. Stir in the 1 teaspoon vanilla extract.
05 - Gently fold in the 1 cup all-purpose flour and 1/2 teaspoon salt until just combined. Be careful not to overmix the batter to maintain a fudgy texture.
06 - Pour the brownie batter into the prepared 9x13-inch baking pan and spread it evenly. Bake for 25–28 minutes, or until a toothpick inserted into the center yields moist crumbs. Allow the brownies to cool completely in the pan on a wire rack.
07 - For the praline topping, melt the 1/2 cup unsalted butter in a medium saucepan over medium heat. Stir in the 1 cup packed light brown sugar and 1/3 cup heavy cream. Bring the mixture to a gentle boil, then reduce heat and simmer, stirring constantly, for 2 to 3 minutes.
08 - Remove the saucepan from heat. Whisk in the 1 cup sifted powdered sugar, 1 teaspoon vanilla extract, and a pinch of salt until the mixture is smooth. Gently fold in the 1 1/2 cups toasted chopped pecans.
09 - Pour the warm praline topping evenly over the completely cooled brownies. Gently spread it to cover the entire surface. Allow it to set at room temperature for 30 to 40 minutes, or until the topping becomes firm.
10 - Using the parchment paper overhang, carefully lift the cooled and set brownies from the pan. Transfer to a cutting board, cut into desired squares, and serve.