Chop some spring onions, including the green bits. Put them into a pan with ½ pint milk and simmer for 20 minutes while you boil some potatoes. When the potatoes are ready mash them and as the lumps disappear add the milk and spring onions –adding extra milk if you need to. Season. Divide the mixture between individual plates – and place a lump of butter in the middle of each portion – you are meant to dip each forkful into the pool of butter before eating.