The sirloin cut of beef is prized for being one of the more underworked and tender areas of the cow, wedged between the ribs and well-muscled rump. Many chefs prefer to serve these cuts as tenderloin roasts and delectable steaks with names like T-bone and porterhouse. Others chop this meat into bite-sized cubes and make it the star of a soup full of vegetables and hearty flavor that might as well be called a stew.
Sirloin soup is usually stocked with tender sirloin meat that braises delectably in a soup, but using tips from other beef primals, or even other animals, would not be unprecedented. A true sirloin soup, however, will have sirloin cuts. These could be packaged as "tri-tip" roasts, beef tips or steaks with names like triangle, porterhouse, T-bone, top sirloin, club, couleotte or flat-bone. Those cuts marked as top sirloin, from the region closest to the spine, have the tenderest reputation.
A soup that features a prized cut of steak often starts with the beef tips getting a quick sear in a hot, oiled soup pot, along with complementary ingredients like garlic, onion, salt and pepper. This locks in flavor and caramelizes the outside of the chunks. Once the outside is lightly charred, beef stock can be poured into the pot to deglaze and then simmer for at least a half-hour. Some chefs also sprinkle the chunks with flour just before the stock goes in as well as any number of other spices like oregano, bay leaf, coriander or basil.
Various vegetables can be added to complement sirloin soup. Some of the more common are carrots, potatoes, celery and mushrooms. Since these vegetables each cook at a slightly different rate, they should be added in order from carrots and potatoes to celery and mushrooms near the end of a simmer, which generally lasts about a half-hour. The chunks all should be cut into same-size pieces to ensure each is cooked through consistently. As the vegetables near the point of fork-tenderness, tomato paste can be added to thicken the broth and add a slight tang.
Many forgo a westernized approach to sirloin soup for something else. A recipe with an Asian flair, for instance, might forgo the tomato paste in favor of ingredients like noodles, sprouts and green onions as well as seasonings like fish paste, soy sauce, lemongrass, ginger, garlic and cilantro. Others may forgo the soup all together and do what cattlemen recommend: using the grill. Before doing this, many dry-rub the sirloin with any number of flavor-enhancing seasonings like garlic salt, cayenne pepper, mustard powder and brown sugar. Another option is to use a marinade concocted of similar ingredients.