chocolate frosted yellow sour cream sheet cake

Ingredients For chocolate frosted yellow sour cream sheet cake

• 1 box

  duncan hines yellow cake mix
• 8 oz

  sour cream
• 1/2 c

  vegetable oil
• 1/4 c

  sugar
• 1/4 c

  water
• 4 lg

  eggs
• FROSTING
• 3

  squares unsweetened chocolate
• 1/4 c

  butter
• 4 c

  powdered sugar
• 1/8 tsp

  salt
• 1/3 c

  milk
• 1 tsp

  pure vanilla extract
• 1 c

  mini chocolate chips ( these get sprinkled on top of cake batter just before baking)