Yields about 1 gallon (serves 16)
Total Time: 4 hours 45 mins (minimum)
2 pounds beef marrow bones, cut into 2-inch lengths (they can have some meat and fat clinging to them)
1½ tablespoons Kosher salt, more to taste
½ teaspoon whole black peppercorns
1 black cardamom pod (optional)
1. Heat an oven to 450 degrees. Rinse the bones briefly in cold water and spread them out on a large rimmed baking sheet. Roast the bones until beginning to brown and sizzling, about 20 minutes.
2. Put the roasted bones in a large pot with about 1½ gallons water, 1½ tablespoons salt, the pepper, and cardamom if using. Cover the pot, bring to a boil, lower the heat, and simmer the soup until rich and beefy, 4-6 hours, skimming off any scum that forms on top (but not the dense fat from the bone marrow). Season to taste with more salt, if necessary.