Remove the cake from the box, but leave it in its clear bag. Massage the bag to break the cake and icing into crumbs, then empty into a bowl.
Using your hands, roll the cake crumbs into 12 balls in three different sizes: 4 x 4cm wide, 4 x 3cm wide and 4 x 2cm wide. Slightly flatten the top and bottom of each 4cm and 3cm ball and the bottom of each 2cm ball. Put on a plate and freeze for 10 minutes.
Melt the chocolate cake covering in a heatproof bowl set over a pan of simmering water. Put the coconut in a separate bowl. Using a fork, dip each ball into the melted chocolate to coat evenly. Shake off the excess and roll in the coconut to cover. Leave to set.
Dip one flat side of a large ball into the melted chocolate and stick to the inside of a jam jar lid. Dip one flat side of a medium ball into the melted chocolate and stick to the large ball and top with a chocolate-dipped small ball. Repeat to make 4 snowmen in total.
Dip the jelly triangles into the chocolate (you may need to melt it again) and stick one onto each snowman for the nose. Draw on a face and buttons with the chocolate flavour icing. Leave to set, then carefully lower an upturned jam jar over each snowman, and screw on. Decorate the jars with ribbon and a gift tag.
These can be made up to a week before giving.
See more Christmas dessert recipes