First, Make The Cookie Layer:

1. Preheat Oven & Prep Pan. To start, preheat the oven to 350 degrees F. Line a metal 8×8 baking pan with parchment paper and set aside.
2. Cream Butter & Sugar. In a large mixing bowl or the bowl of a stand mixer, cream butter, brown sugar, and granulated sugar 2-3 minutes until light, fluffy, and creamy. Scrape down the sides of the bowl.
3. Add Egg & Vanilla. Next, add the egg, then the vanilla, mixing until fully incorporated.
4. Add Dry Ingredients. Scrape down the sides of the bowl and add gluten-free flour, baking soda, and salt. Mix until almost fully blended, with just a few floury patches left.
5. Add In Chocolate Chips and mix until just fully combined and no dry patches remain. The cookie dough will be softer than what you might be used to, but DON’T add extra flour! This softer, more batter-like texture is what helps it bake evenly.
6. Divide Dough. Using rough estimates (this doesn’t need to be perfect), divide the dough so you have 2/3 of the dough set aside for the bottom layer and 1/3 of the cookie dough for the top.

Then, Make The Brownie Batter

1. Melt Butter & Chocolate. In a small saucepan on low heat, or in a microwave-safe bowl, gently melt the butter and chocolate until completely smooth and glossy. (I prefer to do this on the stove)
2. Beat Sugar, Egg & Vanilla. In a medium mixing bowl, combine granulated sugar, egg, and vanilla extract and mix for a full 2-3 minutes until the sugar is dissolved. The mixture should be lighter in texture and color, and if you rub the mixture between your fingers, you shouldn’t really feel any grains of sugar. DON’T RUSH this step or your brownies will not have glossy tops.
3. Add Chocolate Mixture to Egg Mixture and stir until fully blended.
4. Then, Add Dry Ingredients. Next, add the glute-free flour, cocoa powder, and salt and stir until just blended and no dry patches remain.

Assemble & Bake Your Brookie Bars:

1. Start With Cookie Base. Use 2/3 of the cookie dough and pat it out into as even a layer as you can in the bottom of your prepared baking dish. (The dough will not perfectly cover the bottom, and small gaps or openings are totally fine.)
2. Cover With Brownie Batter. Pour the brownie batter over the cookie dough base layer and smooth the brownie batter into an even layer.
3. Top With Blobs of Cookie Dough. Then, divide the remaining 1/3 of the cookie dough into small 1-ish Tablespoon sections and flatten them out with your fingers into small discs, about 1/4-inch thick or so. (Irregular shapes are totally fine!) Press these little dough discs down into the brownie batter so the surface is fairly even. These cookie dough blobs should look like little islands in the brownie batter.
4. Sprinkle With 2 TablespoonsChocolate Chips. 
5. Bake Uncovered 20 Minutes. Place the pan in the oven and bake uncovered for 20 minutes. The tops of the cookie sections will be golden brown at this point.
6. Loosely Cover With Foil & Bake 4-6 Minutes More. To prevent the cookie from burning, loosely cover the pan with foil (no need to seal the sides!) and bake an additional 4-6 minutes to let the cookie bars finish baking. I like my brookies to have a fairly fudgy texture (like brownies!), so I pull them out on the earlier side. If you want yours more cooked through, you can bake them longer.
7. Cool Completely Before Slicing. Let the bars cool in the pan on a wire rack until completely cooled before cutting them into bars.
8. Serve & Store. Enjoy right away or store in an airtight container 2-3 days at room temperature or 2 months in the freezer.