Gently fry the spring onions and garlic in the butter over low heat for three minutes. Now add the peas, water, stock and pepper. Cover and cook over low heat for 10 minutes. Remove from heat and add the herbs. Blitz in your food processor or with a stick blender until smooth.
Put back on the stove just to heat through again. Just before serving, stir in the yoghurt, add the lemon and a pinch of salt. The stock is salty, so first taste and then add, but you WILL need an extra touch of salt (remember, it enhances flavour!).
Serve scattered with a few mint, watercress and parsley leaves for an extra burst of herby flavour. For an over the top girlie-pretty presentation, you can also add some snow peas, feathery sprouts and some edible flowers like pansies. This will serve two people as a main or four as a starter.