Dark Chocolate Cake (Doctored!)

1 Chocolate cake mix
3 T. cocoa
1/2 C. semi-sweet chocolate chips
1 t. vanilla extract
3 eggs, beaten
1/2 C. butter, melted
1 1/3 C. milk

Combine all ingredients.
Mix well. Pour batter into 9x13 greased pan.
Bake at 350 degrees F for 30 minutes.