I used to like the Chinese-style treatment, where one
uses it like a flank steak:
--mm
Beef with mushrooms and onions
cat: mine, main, mean
servings: 4

1 lb mushrooms
1/2 lb onions
oil
salt
1 lb hangar steak
1 clove garlic, mashed
2 Tb soy sauce
1 Tb sake or dry sherry

Clean and slice mushrooms. Dry saute over high heat until
browned. Remove and set aside.

Slice onions thin. Saute in a small amount of oil over high
heat until soft; lower heat to minimum, salt, and allow to
caramelize. Add to mushrooms.

Slice hangar steak on the bias, teasing meat off the big
gristly sheet in the middle. I of course fry this gristle
separately for "cook's treat" - it is perhaps 15-20% of the
total weight of the thing. You see this cut (diaphragm?) on
menus and labels as "hangar" and "hanger." I don't know which
is right. This is a very tasty but troublesome cut and is quite
expensive in NYC - rivaling sirloin in price at times (this was
$6.49/lb - I don't know where I'd seen flank steak recently for
$3.99, but flank is almost equivalent (hangar is somewhat more
savory but has the gristle) and makes a most satisfactory
substitute. Marinate in garlic, soy, and wine for at least 30
min and then saute in a little oil over highest heat.

Combine with onion-mushroom mixture and serve with rice.

Source: moi, August 2001

---
but lately, becoming an adherent of the less is more credo,
I treat the cut even more simply. Marinade is superfluous.

I take the meat with the gristle cut out, rub a cut clove of
garlic over it, salt it, pat it dry as possible. Heaviest
frying pan in the house, heated as hot as possible. Strew a
little salt in the bottom of the pan and lay the meat on top.
Cook a couple minutes, flip, and cook a couple minutes more
for the way I like it (very rare). Slice into thin sheets,
the knife at a very shallow angle to the cutting board. I've
found that the relation of the cut to the grain of the meat
is not all that important but do tend to cut against the grain
by force of habit.