Melt half the margarine in an ovenproof saucepan / casserole. Add oats, oatmeal and nuts and cook for 3 minutes. Put in bowl.
Chop carrot, mushrooms onion and kidney beans finely (food processor very handy here). Melt rest of margarine, add chopped veg, and cook for 2 minutes. Add the rest of the ingredients, and the oat mixture. Cook for 5 minutes.
Transfer to medium over for 40 minutes.
Traditionally, serve with "bashet neeps" (mashed swede) and "mashet tatties" (mashed potatoes) and copious amounts of whisky. Also goes well with roast onions (put in the oven 10 minutes before the haggis). The fat content can be reduced by halving (or removing) the suet. If this is done, check it isn't getting too dry, and add some veggie stock if neccessary.