01 -
Heat your oven to 350°F (175°C), and line your pan with parchment paper for easy cleanup.
02 -
Melt the butter in a microwave-proof bowl. Stir together the sugar, eggs, and vanilla until combined, then sift in the flour, cocoa powder, and salt. Mix it all up until you have a lump-free batter.
03 -
In a new bowl, beat together the softened butter, white sugar, and brown sugar until creamy. Add in the egg and vanilla, beating until light. Gradually mix in the baking soda, salt, and flour, then fold in the chocolate chips until evenly mixed.
04 -
Spread the brownie batter evenly over the bottom of the pan. Drop spoonfuls of the cookie dough on top, pressing lightly to swirl it into the brownie base to create marbled swirls.
05 -
Bake for 30-35 minutes until the edges are firm but the center still looks a little gooey.
06 -
Take it out of the oven and let it cool completely in the pan. Once cooled, cut it into squares or however you like and enjoy.