In a bowl, mix cake mix, egg, and oil until well combined. Add milk slowly to the mixture. Stir in chips and mix well.
Pour batter into a greased 7 x 11 pan. Bake at 350 for 25-30 minutes. May be a little gooey in the middle but they will set up after a few minutes. Let cool.
Mix all ingredients for frosting until smooth. Spread over bars.