Wash the herbs thoroughly in cold water. Place the sugar and honey in a large saucepan with 1 litre of cold water. Gently bring to the boil, stirring, until all the sugar has dissolved, then take off the heat. Thinly slice the lemons and add to the pan, then pick in the herb leaves, making sure they are completely submerged. Pop the lid on and leave to one side to infuse for 24 hours. The following day, line a fine sieve with muslin over a large bowl (if you don’t have muslin, you can use a sheet of high-quality kitchen paper) and strain the cordial. Pour into a 1.2-litre sterilised bottle or jar (see tip) and drink diluted with water, soda, cava or Prosecco.