Combine milk and vinegar in a bowl. Let stand until milk curdles, about 5 minutes.
Preheat oven to 180 C / Gas 4. Grease 2 12-hole mini muffin tins or line paper cases.
Combine 115g butter, 125g caster sugar and vanilla sugar (or extract) in a large bowl; beat with an electric mixer until smooth and creamy. Add eggs one at a time, beating well after each addition.
Mix flour, cocoa powder, baking powder, bicarbonate of soda and salt in a bowl. Alternate adding flour mixture and curdled milk to the creamed butter mixture, mixing until well blended. Spoon cupccake mixture into the prepared tins or paper cases, filling each 3/4 full.
Bake in the preheated oven until tops spring back when lightly pressed and a skewer inserted in the centre of 1 cupcake comes back clean, about 14 minutes. Cool in the muffin tin for a few minutes, then transfer to a wire rack to cool completely, about 1 hour.
Combine cream cheese and 55g butter in a bowl; beat with an electric mixer until well combined. Mix in vanilla extract. Stir in icing sugar gradually. Add a few drops of orange food colouring and mix well to combine.
Transfer icing in a piping bag fitted with a grass tip nozzle. Hold the pastry bag at a 90-degree angle near the top surface of a cupcake. Squeeze bag to form orange 'fur' by pulling tip up and away when the icing strand is about 1cm high. Repeat to cover cupcake evenly with fur.
Add 2 eyes to each cupcake. Cut dried mango into small strips and arrange in the icing as 'horns'.