1. Preheat your oven to 350°F (175°C) and line an 8×8-inch baking pan with parchment paper, letting the edges hang over for easy removal.
2. Start with the brownie layer: In a large bowl, whisk together the melted butter and granulated sugar until combined and glossy.
3. Add the eggs one at a time, whisking well after each addition. Stir in the vanilla extract.
4. Sift in the cocoa powder, 1/2 cup flour, baking powder, and salt. Gently fold the dry ingredients into the wet mixture until just combined—don’t overmix. Fold in 1 cup of chocolate chips.
5. Pour the brownie batter evenly into the prepared pan, smoothing the top with a spatula. Set aside while you prepare the cookie layer.
6. In a separate bowl, cream together the softened butter and brown sugar until light and fluffy, about 3 minutes with a hand mixer or stand mixer.
7. Add the egg and vanilla extract to the cookie mixture and beat until combined.
8. Sift in the remaining 3/4 cup flour, baking soda, and salt. Fold until just mixed, then stir in 1/2 cup chocolate chips.
9. Drop spoonfuls of the cookie dough over the brownie batter. It won’t cover the entire surface, but that’s okay! The cookie dough will spread as it bakes, creating that perfect marbled effect.
10. Bake for 25-30 minutes, or until the edges are set and a toothpick inserted into the center comes out with a few moist crumbs.
11. Allow the brookies to cool completely in the pan on a wire rack. Use the parchment paper edges to lift them out, then cut into squares.

One quick note: When my kids are involved, I let them drop the cookie dough spoonfuls on top—it’s a fun little kitchen moment that always ends in giggles and, of course, a bit of dough on the floor.