You can stuff and roast a heart very nicely, with mixed breadcrumb stuffing. First, take out some of the tough sinews from the heart cavity. I save the crusts from all bread, grate and store in a jar in the freezer not to pick up freezer odours. Then for a stuffing add butter, savoury salt and pepper to taste, pack in as much stuffing as you can get in, keep closed with a skewer or sew it shut (no fancy stitches needed here!) and roast at a slightly slower temp than a regular roast of beef. Heart is 'close' meat as my grandfather used to say and can get tough if roasted at too high a heat. A little broth or water in the roasting pan helps too
Another thing you can do with heart is use it as ground meat - again take out the tough bits then grind in a food processor or old fashioned meat grinder (don't know if you can get them any more, maybe in a thrift shop! Adele Davis a health food author of the last century used to call this recipe half-hearted hamburgers. My kids liked them as much as any other meat patties.
All the boiling, simmering and stewing recipes listed here would be great. Pot roast with lots of onion carrots, turnip and potatoes is great.
Heart is a great source of protein, delicious and relatively inexpensive, valued in many cultures. Congrats to you and your boyfriend for being open to new foods, I'm usre you will find this one a real taste treat.