Preheat oven at 180 degrees and prepare a muffin tin with cup cake cases.
Beat together sugar, margarine, eggs and milk with a hand whisk.
Slowly add flour and cinnamon.
Fold in berries.
Divide into cases and bake for 18-20 minutes.
When cool make the topping by beating together the butter/margarine, icing sugar and blue food colouring.
Pipe in swirls and top with blueberries to decorate.
Recipe courtesy of Wendy McDonald, Inside the Wendy House