This section is from the book "The White Ribbon Cook Book", by Kathryn Armstrong. Also available from Amazon: The White Ribbon Cook Book.
One bullock's heart, 1/4 lb. suet, 6 oz. bread crumbs, 1/4 pt. of milk, 1 tablespoonful of chopped parsley, 1 dessertspoonful of chopped mixed herbs, 1/4 lb. of dripping or butter, 1 pt. of gravy or beef-tea. For the sauce: One small onion, a dessertspoonful of flour, salt and pepper, butter the size of an egg, a large spoonful of mushroom catsup.
Wash the heart in saltwater, taking care to remove all the blood; wash in second water and dry with a clean cloth; be careful to dry it thoroughly; chop the suet as finely as possible, mix with some bread crumbs the suet, parsley, herbs, salt and pepper; lastly, put in the milk, then proceed to fill all the cavities of the heart with the stuffing; take a piece of paper, grease it well with butter or dripping, place this over the cavities and tie it on tightly with string; put 1 oz. of dripping into the pan, and baste the heart occasionally; when gravy boils, cut up the onion, sprinkling with pepper and salt, and add to the gravy; allow it to stew gently until about 5 minutes before the heart is done; skim occasionally; when done strain the liquor; into another saucepan put the butter, and allow it to melt a minute or two; then add the flour and mix smoothly together; then pour in slowly the liquor, stirring until it boils and thickens. Then dish up, remove paper, and add to the sauce the mushroom catsup. Immediately pour this sauce round the heart and serve.
 
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