Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13 inch baking dish.
Step 2
In a large bowl, combine the cake mix, milk, butter and egg; mix until well blended. Batter will be thick. Stir in the chocolate chips. Stir in the walnuts if desired. Spread the batter evenly into the prepared pan.
Step 3
Bake for 25 to 30 minutes in the preheated oven, until brownies spring back to the touch. Cool before cutting into squares.