We've used Growing Communities salad here (of course!) but this is also good with watercress or other peppery leaves

Ingredients

500g new potatoes, washed (no need to peel) 
1 bag Hackney or Dagenham salad, washed
3 celery stalks, sliced
handful fresh mint leaves, torn up
100g Greek-style yoghurt
1 tbs lemon juice
1 tsp wholegrain mustard
salt and pepper to taste

Method

Place potatoes in a saucepan with cold water. Bring to the boil then cook for 15 minutes or until tender. Drain, cool and chop into bite-size chunks. Put the potato pieces, salad leaves, celery and mint in a bowl. Mix the yoghurt, lemon juice and mustard in a small bowl with salt and pepper to taste. Drizzle over the salad, toss to combine everything and serve.