Thai Hot and Sour Chicken Soup

Ingredients:

3 cups chicken stock
4 slices fresh ginger
4 kaffir lime leaves, torn (substitute with lime peel)
2 stalks lemongrass, cut into 2" lengths and bruised (substitute with lime peel)
1 fresh hot chile pepper, sliced (I used 2 large slices)
1/2 pound skinless, boneless chicken, cut into bite-sized pieces
1 cup cherry tomato (or 1 whole tomato, cut into wedges)
One 15-oz can straw mushrooms (or handful fresh sliced mushrooms)
3 tablespoons fish sauce
1 lime, squeezed (about 2 tablespoons lime juice)
fresh cilantro leaves

Directions:

In a pot, add the chicken stock, ginger, kaffir lime, lemongrass and chile slices. Bring to a simmer, cover, and then turn the heat to low. Let simmer for 10 minutes. Strain out and discard the spent herbs. (You can taste the soup at this point, if you would like it more spicy, keep the chile pepper slices in the stock and discard just before serving.)

Add in the chicken pieces, cherry tomato and mushrooms. Bring back to a simmer on medium heat and then cook for an additional 5 minutes.

More info and source : http://www.steamykitchen.com/28246-thai-hot-and-sour-chicken-soup-recipe-video.html