Add the lamb shank and brown on all sides. Place in slow cooker. Add chicken broth, garlic and peppercorns; cover and cook on High for 2 hours.
Add bacon to same skillet in which lamb was browned and cook until crisp.
Add half the stew meat to pan and brown on all sides. Add browned stew meat to slow cooker.
Add onion and remaining stew meat to skillet and cook until meat is browned on all sides. add more if needed. Place remaining browned meat mixture in slow cooker.
Cover and cook on high for 3 hours more.
During the last 30 minutes of cooking, add carrots, celery and beans, and stir in cornstarch mixture. Before serving season with salt and pepper and garnish with chopped fresh parsley , wilted celery leaves, or other herbs.