Step 1: Preheat the Oven and Prepare the Pan

1. Preheat your oven to 350°F (175°C).
2. Line a 9×9-inch baking pan with parchment paper, leaving some overhang on the sides for easy removal. Lightly grease the parchment paper with nonstick spray or butter.

Step 2: Make the Brownie Layer

1. Melt the Butter and Chocolate: In a microwave-safe bowl, combine the butter and chopped semi-sweet chocolate. Microwave in 20-second intervals, stirring between each, until fully melted and smooth. Let cool slightly.
2. Whisk the Sugars and Eggs: In a large mixing bowl, whisk together the granulated sugar, brown sugar, eggs, and vanilla extract until smooth and slightly pale.
3. Combine the Wet and Dry Ingredients: Add the melted chocolate mixture to the sugar-egg mixture and whisk until fully combined. Sift in the flour, cocoa powder, and salt, and gently fold the ingredients together using a spatula until just combined (avoid overmixing).
4. Spread in Pan: Pour the brownie batter into the prepared baking pan and spread it evenly with a spatula.

Step 3: Make the Cookie Layer

1. Cream the Butter and Sugars: In a medium mixing bowl, use a hand mixer or stand mixer to cream together the softened butter, granulated sugar, and brown sugar until light and fluffy (about 2-3 minutes).
2. Add the Egg and Vanilla: Beat in the egg and vanilla extract until fully incorporated.
3. Mix the Dry Ingredients: In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the dry ingredients to the wet mixture, mixing just until combined.
4. Stir in Chocolate Chips: Fold in the chocolate chips using a spatula.

Step 4: Assemble the Browkies

1. Scoop spoonfuls of the cookie dough onto the brownie batter, spacing them evenly across the surface. Use a spatula or your fingers to gently spread the cookie dough into an even layer. It’s okay if it doesn’t cover the brownie layer completely—this creates a marbled effect when baked.

Step 5: Bake the Browkies

1. Place the pan in the preheated oven and bake for 30-35 minutes, or until the cookie layer is golden brown and a toothpick inserted into the center comes out with a few moist crumbs (not wet batter).
2. If the top starts to brown too quickly, cover the pan loosely with aluminum foil for the last 5-10 minutes of baking.

Step 6: Cool and Slice

1. Remove the pan from the oven and let the browkies cool completely in the pan on a wire rack (about 1 hour). This allows the layers to set and makes slicing easier.
2. Once cool, lift the browkies out of the pan using the parchment paper overhang. Transfer to a cutting board and slice into 16 squares or bars.