This marble brownie recipe is perfect for anyone who loves a rich and chocolatey dessert. These brownies are made with all-purpose flour, unsweetened cocoa powder, salt, unsalted butter, granulated sugar, eggs, vanilla extract, and chocolate chips. The brownie batter is divided into two parts, and one part is mixed with more cocoa powder to create the chocolate batter. The two batters are then swirled together and baked to create a beautiful swirl pattern. These brownies are fudgy, moist, and have a delicious chocolate and vanilla flavor. They're perfect for any occasion and are sure to satisfy your sweet tooth.