Boil the meats for an hour, then allow to cool. When cool, grate the liver and finely chop the other meats. Finely chop the suet. Toast the oatmeal in a shallow pan in the oven, shaking occasionally. Mix the meats, suet, onions and oatmeal together with a cup of the stock in which liver and meats were cooked. Add salt and plenty of pepper to taste.
Turn into greased Pyrex bowl, then cover with two or three layers of foil. Steam on a rack in a pan of boiling water for two hours, adding more water as it boils away.
Serve with mashed neeps and tatties. You can jazz up your mash by softening two finely chopped onions in butter, then add pinhead or medium oatmeal until toasted, and stir into the mash along with some cream. Delicious.