For the cupcakes: heat the oven to 160°C (140° fan) 325°F gas 3. Place paper cases in a 12 hole bun tin.
Beat together all the ingredients in a mixing bowl until smooth.
Spoon into the paper cases and bake for 20-25 minutes until golden and springy to the touch. Place on a wire rack to cool completely.
To decorate: Divide the marzipan into 6 equal portions. Knead a few drops of food colouring into each portion until evenly coloured.
Roll out the green marzipan thinly on a surface lightly dusted with icing sugar and cut out 12 leaf shapes using a cookie cutter or a card template.
Roll out 1-2 portions of another colour as before and cut out stocking shapes using a cookie cutter or a card template.
Roll out the remaining coloured marzipan thickly and cut into cubes for the 'parcels'.
Brush the cakes with the warmed jam and attach the decorations.
Pipe the decorative details with white piping icing and leave to set.