Rinse the stomach thoroughly and soak overnight in cold salted water.
Rinse the liver, heart, and tongue
. In a large pot of boiling, salted water, cook these parts over medium heat for 2 hours. Remove and mince
. Remove any gristle or skin and discard.
In a large bowl, combine the minced liver, heart, tongue, suet
, onions, and toasted oats
. Season with salt, pepper, and dried herbs
. Moisten with some of the cooking water so the mixture binds. Remove the stomach from the cold salted water and fill 2/3 with the mixture. Sew or tie the stomach closed. Use a turning fork to pierce the stomach several times. This will prevent the haggis
In a large pot of boiling water, gently place the filled stomach, being careful not to splash. Cook over high heat for 3 hours.
Serve with mashed potatoes
, if you serve it at all.