My favourite way to do heart for heart's sake is in a slow cooker. Cut it into reasonable sized chunks (you need a large knife and a lot of clout), add a little water, red wine and seasoning, and put on to cook at breakfast time. By dinner, it's soft and tender and juicy and good, and there's a really nice gravy too.
Mrs Beeton didn't have a slow cooker, alas. Not that a Victorian oven or aga couldn't be persuaded to act like one, but her only recipe for ox heart is to have it stuffed.
Beeton's Bullock's Heart
1 ox heart. The younger than animal, the more tender, but the bigger the more economical!
2 oz bacon
1/2 a lemon rind
6 oz breadcrumbs
1 teaspoon parsely
1 teaspoon mixed herbs
salt, cayenne and mace to taste (about 1 teaspoon in total)
Larding Needle and twine (or string and a spare pair of hands)
Lots of time.
Put the heart in warm water to soak for two hours.
Chop finely the bacon, suet, herbs and lemon peel together. Or run them all through a mincer.
Add seasoning and blend with breadcrumbs.
Wet to make it a little sticky.
Beat the eggs and add them to the mix. Make it very sticky.
Wipe the heart with a cloth. Use your sharp knife to cut away the lobes and gristley bits.
Stuff with the mix, and sew it up (or tie it tightly).
Wrap in foil and put in a hot oven. Depending on the size of the heart, this could take another couple of hours.
Baste it regularly with stock or fat. before serving, baste it again and leave it to sit a couple of minutes. Good with gravy or redcurrant sauce. It'll probably feed about 8 people, so have some mates over!
Beeton, Isabella; Mrs Beeton's Book of Household Management; mrsbeeton.com; 2007