Preheat the oven to 170C.
Cut the heart into 2cm pieces, place in a bowl and season. Heat half the oil in a large ovenproof casserole and fry the heart for 4-5 minutes. Add the remaining oil and vegetables and cook for 3-4 minutes. Sprinkle over the flour and stir in the remaining ingredients.
Cover and place in the oven for 1½ hours. To prepare the dumplings stir the flour, salt, suet and herbs together in a large bowl. Add enough water to make a smooth dough that’s not too sticky. Divide into 8 even-sized balls.
Twenty minutes before the end of cooking, remove the lid from the casserole and sit the dumplings on top, return to the oven for the final cooking time. Serve.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.