Put the potatoes in a pan of lightly salted cold water. Bring to the boil then simmer for about 15 minutes until they are tender. Add the peas and a couple of mint leaves for the last 3-5 minutes of the cooking. Drain, then transfer the peas and potatoes into a serving bowl. Remove the mint leaves.
Cut the bigger potatoes into bite-sized pieces, the add the minced garlic, spring onion pieces, olive oil, lemon juice and cider vinegar.
Season to taste, toss well. Taste, and adjust the oil/vinegar to your liking. Keep warm or let it cool completely.
Shred the mint leaves and add to the salad just before serving.