2 cucumbers (approx 700g/1lb 9oz)
½ bunch dill (about 10g/⅓oz), finely chopped
3 tbsp elderflower cordial
1 medium–large red onion (approx 150g/5½oz), sliced into very thin rounds
1 tsp wholegrain mustard
3 tbsp extra virgin olive oil, plus extra to taste
3 tbsp red wine vinegar
120²µ/4¼´Ç³ú feta (optional)