Pre-heat oven to 180°C (160°C fan-forced). Line 12 ½ cup capacity muffin pans with paper cases.
Place butter and sugar into the bowl of an electric mixer, beating until pale and creamy. Add eggs one at a time, mixing well between each addition. Mix in vanilla.
Fold in combined flour, cocoa and cinnamon, alternately with the milk until all combined and mixture is smooth. Fold in currants. Spoon mixture between patty cases and bake for 20 minutes until just cooked and top springs back when pressed. Remove to a cooling rack to cool completely.
For the Icing; Place milk in a microwave safe jug and microwave on medium heat for 45 seconds until hot. Add chocolate melts and stir through until melted and smooth. Whisk in the icing sugar. Spread over cooled cakes, leaving a couple tablespoons of icing for decorating.
Arrange the pretzel on each cupcake to create antlers. Place two white melts on each cupcake to create eyes, use the remaining icing to attach the currants to create pupils. Place a red Smartie in the middle of the eyes to create a nose.