In the bowl of an electric mixer fitted with the paddle attachment, combine the butter, brown sugar, and granulated sugar; beat until mixture is lightened. Beat in the egg and then the egg yolk. Add the vanilla extract, mixing until well-blended.
Scrape down the sides of the bowl. In a medium bowl, whisk together the 2 1/4 cups flour, baking soda, and salt. Add to the creamed mixture and beat on low speed until just incorporated. Stir in the chocolate chips. Cover and set aside.
Brownie Cookie Dough
Whisk together the sugar and cocoa in a large mixing bowl; set aside. In a microwave safe bowl, heat the butter in 30 second intervals in microwave on 100% power until completely melted (about 1 minute to 1 minute 30 seconds total). Pour butter into the bowl with sugar and cocoa; stir until smooth. Add the eggs to mixture one at a time, stirring after each addition until completely incorporated. Stir in the vanilla. Add the flour, baking powder and salt; stir until well combined. Cover and set aside.
Preheat the oven to 375°F. Line two baking sheet with parchment paper.
Roll the Doughs and Bake
Using a small cookie scoop (4 teaspoon capacity) portion out all of the chocolate chip cookie dough onto a cookie sheet. Wash and dry the cookie scoop, then portion out the brownie dough in the same manner. (If you don’t have a cookie scoop, portion dough using measuring spoons, about 1 1/2 level tablespoons for each dough ball.)
Press a chocolate chip cookie dough ball and brownie dough ball together and roll between your palms into a ball. Repeat with remaining dough balls. Place each dough ball about two inches apart on prepared baking sheets, and bake for 10-12 minutes or until well puffed and lightly golden on the edges of the chocolate chip cookie halves.
Remove from oven, and let cool on baking sheets about 3 minutes before moving cookies on to cooling racks to cool completely.
You may have a little chocolate chip cookie dough left over after assembling the brookies. Press two of the chocolate chip cookie dough balls together, roll, and bake for the same amount time as the brookies.To enhance the beauty of the chocolate chip portion of the cookies, dot a few extra chocolate chips on top immediately after you remove them from the oven.
Keyword bronwnies, brookies, chocolate chip cookies, decorated cookies