Preheat oven to 200C (180C fan forced, 400F, gas mark 6). Line a 12-hole muffin tray with paper casings.
To make the cupcakes, place all cupcake ingredients except for milk into a mixer bowl and process until smooth and well combined. Add milk and mix for another 30 seconds or so.
Divide mixture between paper cups. Bake in the oven for 15-20 minutes, remove from oven and allow to cool in the tin for 5 minutes, then on a wire rack.
Meanwhile, prepare the cream cheese frosting. In a large bowl using a handheld or stand mixer beat the cream cheese and butter on high speed until smooth and creamy, about 2 minutes. Add icing sugar, vanilla and milk. Beat on low speed for 30 seconds, then on high speed for a further 2 minutes.
Once the cupcakes have cooled down completely, spread the icing with a palette knife or butter knife on top of the cupcakes.
To pipe, optional, spoon mixture into a medium zip lock bag, twist and push out any air. Tie the end tightly with a rubber band. Cut off the tip and pipe onto the cooled cupcakes.