1. Toast oatmeal slowly and evenly under the grill until crisp.
2. Mix all the remaining ingredients (except for the stomach bag) together.
3. Pack the mixture into the stomach bag to just over half full, press out the air and sew up securely with kitchen string.
4. Prick the haggis all over with a large pin to prevent it bursting. You can wrap it with foil if the stomach appears weak in places. Drop into a large pot of cold water, bring to the boil, reduce the heat and simmer gently for about 3 hours.
5. Serve with clapshot: mashed potatoes and turnips.