This is a Thai Soup with shrimp that is fairly common. I made adjustments to the recipe to remove the lemongrass (hard to find) and galangal. But, if available, add some ginger and some basil leaves too. I tried to simplify the recipe with easier ingredients and faster cook time.
Tom Yum Goong
6-12 Large peeled shrimp (approx. 1/2 - 1 pound)
6 cups Chicken stock
2-4 Thai chiles (adjust for heat level desired)
3-4 med. Kaffir lime leaves (or other lime leaves)
2-3 stalks green onion
3-6 tbsp lime juice (test for desired level of sourness)
1-2 tbsp fish sauce
1/2 cup cilantro
2 cups white mushrooms
1 1/2 tsp white sugar
Prepare the chicken stock in a medium size pot, bring to light boil. Reduce to medium heat, add thinly sliced chiles, lime leaves cut into strips and tied with plastic twist-tie (or put into a boil sack), and quartered mushrooms. Stir for a minute or two and taste for spicy and salt balance, then add fish sauce to bring it desired salt level, allow to simmer on med heat for a few minutes. Add 1.5 tsp of white sugar (palm sugar or brown sugar works too) and retaste for spicy, salty, and sweet balance.
Add shrimp and boil for approx 2-3 min just until they turn white, then remove from heat. After removing from heat add cilantro and green onion. Finally add lime juice to bring sour flavor to soup, make any adjustments to salt, spicy, sweet, and sour balance now. Remove lime leaves from pot as they aren't edible in this recipe.