Grease nine holes of a muffin pan. Place chocolate and butter in a heatproof bowl. Sit over a saucepan of simmering water. Stir until smooth. Remove from heat and stir in sugar. Cool for 5 minutes.
Stir in eggs and milk. Stir in combined sifted flour and powders. Divide batter among prepared pan holes (about ½ cup of mixture per hole). Cook in pre-heated oven for about 30 minutes or until cooked when tested. Remove muffins and cool.
To make chocolate icing, place chocolate and cream in a heatproof bowl. Sit bowl over a saucepan of simmering water. Stir until smooth. Remove and cool to room temperature.
Place muffins upside down on a wire rack, sitting over a tray. Pour chocolate icing evenly over muffins. Spread to coat sides.
To make reindeer faces, trace nine ovals 3cm x 5cm onto a sheet of baking paper. To make eyes, trace 18 ovals, 2cm x 3cm onto baking paper. Turn paper over with trace-side facing down. Spread white chocolate inside traced shapes. Allow to set.
To assemble: pipe mouth onto faces with dark chocolate. Use small dots of chocolate to stick on cherries for noses and cachous for pupils. Squeeze chocolate onto back of eyes and place on muffins. Repeat with faces. Insert pretzel halves in top of each muffin to represent antlers.