1. Line a tray with non-stick baking parchment and spread the chocolate out to a rectangle 30 x 23cm/12 x 9in. Tap the tray against the work surface to level it and leave in a cool place to set firm.
2. Using a 7.5cm/3in metal cutter, stamp out 12 discs of chocolate. Remove the trimmings and keep to one side. Leave the discs to set hard then store in an airtight container interleaved with greaseproof paper or parchment in the fridge for up to 1 week.
3. Line another tray with non-stick baking parchment and re-melt the chocolate trimmings. Make a piping bag with greaseproof paper and fill with the cooled chocolate. Snip off the end and pipe some freehand outlines of small holly leaves or other leaf shapes. Leave to set in a cool place then store as for the discs.
4. To assemble the towers, sandwich two discs together with fromage frais, then pile some fruit on top and decorate with leaves. Serve immediately.