If you cant get fresh peas, buy some frozen peas from the supermarket. To defrost, its best to just leave them out of the freezer overnight, as the peas keep their bright green colour for longer. If you forget, empty them into a bowl and cover with boiling water. Leave for 5 minutes, then strain them and shock in ice water and strain again. Put all the ingredients save the feta in a bowl and squish the peas with your hands to break them up a bit, then add the feta, crumbling it as you go. Season with salt and pepper and another squeeze of lemon juice and more olive oil if you want. Its best to make this fresh - it doesnt keep too well. But if you have leftovers, I eat them with pasta the next day.