Cook the barley according to package directions until tender and cooked through (cooked barley will soak up less of the broth in the soup).
Prep and weigh the beef. Remove any fat or gristle from the meat and chop or shred it into bite-size pieces. Weigh the prepped meat (the goal is to have 1 to 1 1/2 pounds or 2 to 3 cups) and supplement with additional meat or mushrooms. (See recipe notes for options.)
Prep the leftover potatoes and carrots by dicing them into bite-size pieces. Measure the amount of prepped potatoes and carrots (the goal is to have 2 cups of potatoes and 1 cup of carrots).
Measure the leftover gravy and mushrooms (the goal is 1 ½ cups which usually works out to 1 cup of gravy and ½ cup cooked mushrooms). Make up the difference with beef marrow bones or make more gravy with mushrooms (see notes).
Prep all the fresh vegetables (cauliflower and supplements), onion, garlic, and parsley, and defrost the frozen peas.
MAKE THE SOUP:
In a large soup pot over medium heat, add the oil, onion, and celery. Cook, stirring occasionally, until onions are translucent and edges begin to brown, about 8 minutes.
Add the cauliflower and any uncooked vegetables used to supplement the leftover potatoes and carrots—along with the garlic, dry herbs, salt, and pepper. Cook until vegetables soften (add oil as needed), about 10 minutes.
Add the broth, bay leaf, and Parmesan rind to the vegetables and bring to a low boil. Stir in the gravy, tomatoes, peas, (leftover) cooked vegetables, barley, and meat. Bring to a simmer and cook for 30 minutes to meld flavors.
Stir-in parsley the last 5 minutes of cooking, and adjust seasoning for salt and pepper, to taste. Serve hot.
Video
Notes
Supplement the beef in one of the following ways: (SEE RECIPE POST FOR DETAILS)
Canned roast beef
Grocery deli cooked beef—every deli has different prepared foods like roasted beef, brisket, or stew.
Raw beef—I recommend tender cuts like tri-tip steak or velveting low-grade sirloin since tougher cuts of beef like chuck roast won’t have the time to get tender in this quick-simmered soup.
Chopped portobello mushrooms—for the best flavor, cut the mushroom pieces a little bigger than the meat (they shrink when cooked).
Supplement the leftover potatoes and carrots with fresh potatoes and carrots, or make up the amount with fresh parsnips, celery root, cauliflower, eggplant, zucchini, green beans, mushrooms, or frozen mixed vegetables.Supplement the leftover gravy and mushrooms in one of the following ways:
Add 2-3 beef marrow bones to the soup and 1 teaspoon of beef bouillon—beef marrow provides a velvety-rich texture.
Make more gravy and skillet-browned mushrooms. (SEE RECIPE POST)
TIPS & VARIATIONS:
Save pan drippings from all roasted meats and freeze. Collect these frozen bits in a freezer-safe zip-type bag to boost flavor in soups or gravies.
Save leftover beef portions that are too small for a full meal from various recipes—roasts, stews, grilled steak, brisket, fajitas, etc.—collect these smaller portions to use in vegetable beef soup.
Make your own beef broth from meaty bones for the best soup flavor
Substitute buckwheat instead of barley to make it gluten-free.
Omit parmesan rind for dairy-free
Freeze soup leftovers in freezer zip-type bags for up to 3 months.
If using a pressure cooker, cook for only 8-10 minutes in STEP 3.