Trying to make a "chocolate chip cookie cake" (those really big cookies decorated like cakes)

 My daughter wants a "cookie cake", like the ones they charge too much for at the mall, for her birthday. I have heard that you can use regular choc chip cookie dough and just smoosh it down into a jelly roll pan to make a big rectangular cake.  My concern is how to get it done in the middle and notbe overdone on the edges....  Should I lower the oven temp and let it bake longer?   If anyone has made one of these before I would really appreciate some help!!!

In reading through my Betty Crocker Cookbook (copyright 1986by General Mills, Inc., Minneapolis, Minnesota), chocolate chip bar cookies can be made by pressing the dough into "an ungreased rectangular pan, 13 X 9 X 2 inches.  Bake until golden brown about 25 minutes; cool."  The baking temperature for is 375.  I do not know about using a jelly roll pan, but thought maybe this would work as an option for a good sized chocolate chip cookie cake. 

Here's her recipe:

1 cup margarine or butter, softened

3/4 cup sugar

3/4 cup brown sugar, packed

1 egg

2 1/4 cups all-purpose flour

1 teaspoon baking soda

1/2 teaspoon salt

1 cup coarsely chopped nuts (optional)

1 pkg (12 oz) semisweet chocolate chips

Mix butter, sugars and egg.  Stir in flour, baking soda and salt (doub will be stiff).  Stir in nuts and chocolate chips.