Adapted from parentpretty.com
Box yellow cake mix (I used Betty Crocker)
Small box instant vanilla pudding
Cup vegetable oil
Cup chocolate chips. I used ½ cup holiday mini M&M's and ½ cup milk chocolate chips.
Preheat your oven to 350 degrees. Combine cake mix, pudding, water, vegetable oil, eggs and chips or M&M's in large bowl. Pour the batter (it's going to be thick) into a greased 10x13 baking dish. I sprayed my dish with nonstick cooking spray which worked well. Bake your bars for 20-30 minutes (I took mine out at 25.) It may look sort of raw in the middle but if the edges are just golden and starting to get crispy, it's probably perfect.