Preheat oven to 400 degrees Fahrenheit. Cut the pointy end of the garlic bulbs off and wrap completely in aluminum foil. Roast for about 25 minutes until garlic head become mushy.
Remove from the oven and let cool. Squeeze the garlic cloves into a bowl. Mix in balsamic vinegar, shallots, and marjoram. Place hanger steak in the garlic marinade and refrigerate overnight.
Heat the olive oil a sauté pan placed on medium-high heat. Remove the steak from the marinade and sear the first side for 4-6 minutes. Flip and cook for another 4-6 minutes, or until desired doneness is reached.
Allow the steak to rest for five minutes and slice against the grain.