Beef broth from marrow bones

My parents are visiting this weekend, and to celebrate, I took them out to dinner at my restaurant Friday night. We got burgers, duck fat-roasted fiddlehead ferns, and bone marrow. It was all delicious; there were plenty of leftovers, as those are filling burgers, so we all took doggie bags home.

I also brought home the cleaned-out marrow bones, to use for broth. Three big marrow bones, plus assorted vegetable scrap, plus a little salt, plus water. I let it simmer on low all day, and was rewarded with a deep, rich broth, the color of French onion soup. And man, the house smelled good.

I'll freeze that broth and use it for soups and the like. Close to a gallon of beef broth, for the cost of just taking the bones home.