Heat oven to 350°F (325°F for dark or nonstick pan). On a 13x9 inch pan, rub with shortening and dust with flour.
In large bowl, beat cake mix, water, buttermilk, butter and egg with electric mixer on low speed 30 seconds. Beat on medium speed 2 minutes, scraping bowl occasionally. Stir in 1 1/2 cups of the chocolate chips. Spread in pan. Sprinkle any remaining chocolate chips on top.
Bake 32 - 35 or until toothpick inserted in center comes out clean. Cool completely, about 1 hour. Enjoy!!