Preheat your oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper, leaving an overhang. Spray the bottom and sides with non-stick spray.

In a small saucepan over low heat, melt 1/2 cup butter. Whisk in 1 cup granulated sugar for 1-2 minutes until glossy. Add 2 large eggs, one at a time, whisking thoroughly after each addition. Stir in 1 teaspoon vanilla extract.

In a separate bowl, whisk together 1/3 cup sifted cocoa powder, 1/2 cup all-purpose flour, and 1/4 teaspoon salt. Gradually add this mix to the wet ingredients, stirring until just combined.

Pour the brownie batter into the prepared pan and spread evenly. Set aside.

In a large bowl, cream together 1/2 cup softened butter, 1/2 cup granulated sugar, and 1/2 cup packed brown sugar for 2-3 minutes until light and fluffy. Beat in 1 large egg and then add 1 teaspoon vanilla extract.

In a separate bowl, whisk together 1 1/4 cups all-purpose flour. Gradually add to the wet mixture, mixing on low speed until just combined. The dough should be thick and slightly sticky.

Dollop spoonfuls of cookie dough over the brownie batter. Gently press and spread the cookie dough evenly.

Bake in the preheated oven for 45-55 minutes. A toothpick inserted in the center should come out with moist crumbs.

Remove from the oven and cool completely on a wire rack for 2-3 hours.

Lift from the pan using the parchment overhang and cut into 12 squares. Serve warm or with a scoop of vanilla ice cream.