Ingredients

Step by step

1. Line 2 baking sheets with baking paper. In a food processor, whiz together the butter, sugar, lemon zest and thyme (if using) until light and fluffy. Add the flour, cornflour and a pinch of salt; whiz together until it begins to form clumps. Lightly dust a work surface with a little flour and knead the dough lightly until smooth.
2. Roll the dough out onto a sheet of baking paper until about 1cm thick. Using a 6cm round cookie cutter, stamp out as many rounds as you can, and place on the baking sheets, evenly spaced. Re-roll the trimmings and stamp out the remaining rounds so that you have 18 in total. Prick each one a couple of times with a fork, then chill for an hour or until firm.
3. Preheat the oven to 180°C, fan 160°C, gas 4. Bake for about 10 minutes, swap the trays round and bake for a further 10 minutes until golden. Leave on the baking sheet for 5 minutes, then transfer to a wire rack to cool.
   Tip

   Not an icing queen? These shortbreads are just as delicious uniced, or drizzle them with a simple glacé icing.
4. To decorate, make up the royal icing according to pack instructions until it resembles soft peaks. Transfer 150g of the icing into a bowl and colour black with the food colouring, adding a drop at a time to reach the right shade (about 15-20 drops). Cover the remaining white icing with clingfilm placed directly over its surface, to prevent it drying out. Spoon the black icing into a disposable piping bag, snip off the tip and pipe a line around the edge of each cookie (or use a small plain piping nozzle); leave to dry for 10 minutes.
5. Check the consistency of the white icing (it needs to be thick but spreadable), add a drop of water if needed, then spoon a little icing onto each cookie, using the back of a teaspoon to spread in a circle up to the black edge. Leave for about an hour or until set hard. Use the black icing pen to write on the numbers and hands of a clock face. Leave to dry.