4 cups water
1-2 cups coconut milk(optional)
2 Tbsp Tom Yum paste
Juice of one lime
3 garlic cloves, peeled
4 kaffir lime leaves
6cm pieces of ginger (or galangal)
4 bird's eye chilies, stems discarded
4 Tbsp fish sauce
1 bsp coconut palm sugar
1/2 white onion, cut into wedges
1 cup sliced FreshlyGrounds oyster mushrooms
2 Roma tomatoes, diced
1 cup shrimps/Prawns - add extra if you'd like
1 handful roughly chopped coriander or flat-leaf parsley
Fill a medium-sized saucepan with 4 cups of water. Add torn kaffir lime leaves, roughly chopped lemongrass, ginger, whole garlic cloves, and sliced chilies. Cover, and bring to a boil over medium-high heat.
Let the water boil for about 5 minutes; add tom yum paste and coconut milk (if using). Bring heat to medium-low. Simmer for another 5 minutes.
Add the shrimp, oyster mushrooms, onion, tomatoes, fish sauce, and sugar. Cover, and let simmer for 10 minutes.
During the last five minutes of simmering, add the coriander or flat-leaf parsley, and the lime juice.
Adapted from https://www.killingthyme.net