Combine the beef, barley, mushrooms, celery, carrots, leeks, thyme, beef broth and soy sauce in a slow cooker. Add 1 cup water, 1 teaspoon salt and 1/4 teaspoon pepper. Cover and cook on low, undisturbed, 8 hours. Uncover and skim off any excess fat. Transfer the beef to a cutting board, let cool slightly and slice or shred by hand into bite-size pieces. Thin the vegetable-barley mixture in the slow cooker with some water, if desired. Divide among shallow bowls and top with the beef. Serve with horseradish, if desired.
Photograph by Antonis Achilleos
Courtesy of Food Network Magazine