Champit Tatties with Skirlie

3 1/2 ounces butter, divided
1 medium onion, peeled and finely chopped
3 lbs potatoes, peeled and cut into chunks (choose potatoes for mashing)
2 ounces oatmeal (or whole rolled porridge oats)
nutmeg
7 fluid ounces milk
1 tablespoon fresh parsley, roughly chopped
salt & freshly ground black pepper

1. To make the skirlie, melt 1 1/2 ounces of butter in a medium
frying pan, add the onion and fry very gently for 15 minutes
until soft and browned, stirring occasionally.
2. Meanwhile put the potatoes for the champit tatties in a large
pan of salted water, bring to the boil, cover and simmer for
about 15 minutes until they are tender.
3. When the onions are cooked, mix in the oats, increase the
heat slightly and fry, stirring often, until well toasted and
golden: remove from heat and season with nutmeg, salt and
pepper: set aside.
4. Towards the end of the cooking time for the potatoes, heat
the milk over a low heat (don't boil it).
5. Drain the potatoes and mash them well potatoes then slowly
beat in the hot milk and remaining butter at the same: season
and spoon into a warm serving dish.
6. To serve, reheat the skirlie if necessary, stir in the
parsley then scatter over the tatties.