Here is a recipe from Chef Ming Tsai who presented this wonderful soup on the Dr. Oz Show.  He stated that he eats this all the time and is never sick! It is loaded with good things for the immune system; shiitake mushrooms, ginger, garlic, and chicken broth. Besides that it is yummy.

SHIITAKE HOT AND SOUR SOUP

1 tbsp grapeseed oil

1 jalapeño, minced with seeds

1 tbsp minced ginger

1 tbsp minced garlic

2 bunches scallions, green and white parts sliced, 2 tbsp greens reserved

1 lb shiitakes, stems removed and tops 1/4-in sliced

2 1/2 quarts chicken stock or low-sodium chicken broth

2 tbsp naturally brewed soy sauce

Juice and zest of 2 lemons

1 block silken tofu, cut into 1/2-inch cubes

2 cups shredded carrots

Freshly cracked black pepper

Directions

In a stockpot over medium-high heat, add oil and swirl to coat the bottom. Add jalapeño, ginger, garlic and scallions. Sauté until aromatic, about a minute. Add shiitakes and sauté 2 minutes, until softened.

Add stock and soy sauce, bring to a simmer and reduce by 20%, about 5 minutes. Add lemon juice, tofu and carrots and cook gently for 2 more minutes to heat tofu through. Season with black pepper.

Ladle soup into serving bowls and garnish with reserved scallion greens and lemon zest.