Line a 9 x 13 pan with tin foil.
Mix flour, sugar and cocoa together.
Add egg and oil and mix well.
Pour into prepared pan and spread evenly.
Bake the brownies in a 350 degree oven for 40-45 minutes until the center of the brownies is set.
Let brownies cool completely.
To make the topping, stir malted milk powder, milk and vanilla together in a small bowl until well blended.
Stir in margarine and powdered sugar and mix well.
Spread mixture over cooled brownie layer.
Top with crushed malted milk balls and let set before serving.