Preparation Heat oil in heavy large pot over medium-high heat. Add mushrooms and onions. Sauté until mushrooms brown, about 18 minutes. Add celery and garlic and stir 1 minute. Add beef shank slices and all remaining ingredients. Bring to boil. Reduce heat to medium-low. Cover and simmer until meat is tender, about 1 1/2 hours. Remove from heat. Using tongs, remove meat from pot. Cool slightly. Remove meat from bones; discard bones and any tough connective tissue. Cut meat into bite-size pieces and return to soup. Season soup to taste with salt and pepper. (Can be made 2 days ahead. Cool slightly at room temperature. Chill uncovered until cold, then cover and keep chilled. Rewarm over medium heat.) Note:Porcini mushrooms are available at Italian markets, specialty foods stores and many supermarkets.
Preparation Heat oil in heavy large pot over medium-high heat. Add mushrooms and onions. Sauté until mushrooms brown, about 18 minutes. Add celery and garlic and stir 1 minute. Add beef shank slices and all remaining ingredients. Bring to boil. Reduce heat to medium-low. Cover and simmer until meat is tender, about 1 1/2 hours. Remove from heat. Using tongs, remove meat from pot. Cool slightly. Remove meat from bones; discard bones and any tough connective tissue. Cut meat into bite-size pieces and return to soup. Season soup to taste with salt and pepper. (Can be made 2 days ahead. Cool slightly at room temperature. Chill uncovered until cold, then cover and keep chilled. Rewarm over medium heat.) Note:Porcini mushrooms are available at Italian markets, specialty foods stores and many supermarkets.