Start by peeling the prawns, and separating the prawn fat, prawn meat, and shells.
Heat the lard (or mild oil) in a pot to make the broth base.
Once the oil is hot, add the shallots and sauté until fragrant.
Add the prawn shells and sauté until they turn golden.
Season with salt.
Add the herbs: lemongrass, kaffir lime leaves, and coriander roots.
Pour in clean water and bring to a boil.
Let it simmer for about 1 hour.
Once done, strain out the solids.
Heat lard (or mild oil) in a pan until hot.
Add lemongrass and kaffir lime leaves, stir-fry until fragrant.
Add prawn fat, season with salt, and stir-fry until cooked.
Strain out the herbs.
Place the stock in a pot and season with fish sauce and salt.
Add the kaffir lime leaves.
Add the prawns and cook until they’re nicely done.
Add bird's eye chillies and straw mushrooms.
Squeeze fresh lime juice into the serving bowl.
Pour the hot tom yam broth from the pot into the bowl.
Taste and adjust the seasoning for a tangy flavour.
Finally, add the prawns and mushrooms to the bowl.
Garnish with shredded lemongrass and coriander leaves.
