Preheat your oven to 350°F (175°C) and prepare an 8x8 or 9x9-inch baking pan with parchment paper, lightly greased.

Sift together the all-purpose flour, salt, and Dutch-processed cocoa powder in a medium bowl. Set aside.

In a medium saucepan, combine unsalted butter, canola oil, and ½ cup granulated sugar over medium heat. Stir until melted and combined, about 3-4 minutes.

In a large mixing bowl, whisk together the large eggs, additional egg yolk, and remaining 1 cup of granulated sugar until pale and frothy. Stir in vanilla extract.

Gradually pour the warm butter mixture into the egg mixture, whisking continuously until fully incorporated.

Fold in the dry ingredients until just combined. The batter should remain thick and pliable.

Gently fold in the semi-sweet chocolate chips and any optional add-ins.

Pour the brownie batter into the prepared baking pan and spread it evenly. Bake for 30 minutes in a 9-inch pan or 40 minutes in an 8-inch pan.

Remove from the oven and cool on a wire rack for about 2 hours before cutting into squares.