In a saucepan, combine sauce ingredients and keep warm.
In a bowl, combine flour, sugar, cocoa, baking powder and salt. In a small bowl, combine egg, milk, butter and vanilla; add to dry ingredients and stir until moistened. Fold in chocolate chips. Pour into a greased 1-1/2-qt. baking dish. Pour warm sauce over batter. Do not stir. Bake at 350° for 35-40 minutes or until cake is firm and floats in sauce. Let rest 10 minutes. Serve warm with whipped cream or ice cream.