Heat a skillet over medium-high heat with 1 tablespoon oil. Brown beef shanks 4-5 minutes per side until a deep golden crust forms. Transfer seared shanks to the slow cooker.
3-4 pounds beef shanks, 1 tablespoon oil
Add ½ cup beef broth or red wine to the hot skillet and scrape up the browned bits with a wooden spoon. Pour the liquid over beef shanks in the slow cooker. Then add remaining broth, diced onion, minced garlic, bay leaves, and fresh thyme to the slow cooker.
6 cups beef broth, 0.5 cup red wine, 1 large onion, 4 cloves garlic, 2 bay leaves, 1 bunch fresh thyme or parsley
Cover and cook the soup on low heat for 4 hours in the slow cooker.
Add sliced carrots and chopped celery to the slow cooker. Continue cooking on low for another 2 hours.
3 medium carrots, 3 stalks celery
Stir in cubed potatoes and cook for 1 more hour until beef shanks fall off the bone and potatoes are fork-tender. Using a ladle, skim fat from the surface of the soup.
2 medium potatoes
Remove bay leaves from the soup. Taste broth and add salt, pepper, or a splash of vinegar if needed. Stir in fresh parsley just before serving.
2 bay leaves, 1 bunch fresh thyme or parsley
