Substitutions; first lemongrass... if you cant find it fresh, most grocers will have lemongrass paste. about 1 tsp per stalk of fresh lemongrass will work. Galangal is similar to fresh ginger. A little bolder savory and peppery flavor. Sub ginger and a tbs of black pepper if you cant find it. Traditional recipe calls for kaffir lime leaves. This I couldn't find and subbed with the lime zest. If you can't find thai chillies, add more Chilli paste. Traditionally a Thai roasted Chilli paste is used

Substitutions continued; I could not find the Thai Chilli paste so I used the Salam oelek. If you can't find oyster mushrooms, dried shitake, or portobello mushrooms will work. If you can't find coconut aminos, low sodium soy sauce will work.

Peel the shrimp, place shells in a large soup pot. Set the meat aside for later. Split lemongrass in half lengthwise. Remove the outer layer. Smash and add to soup pot. Cut the ginger or galangal in 1/4 inch thick slices. Smash and add to the pot. Smash thai chillies and garlic cloves. Add to the pot. Add remaining broth ingredients. Bring to a boil over high heat, covered. Then reduce heat and simmer 20 minutes.

After 20 minutes, strain out the solids in the broth and discard. Return the liquid in the pot to a boil.

Coarsely chop mushrooms, tomato, and onion add to soup with the rest of the soup ingredients except the shrimp and mussels. Return to a simmer and cook covered until onion and mushrooms are tender. About another 15 to 20 min.

Next is adding the protein. If using fresh mussels. Remove the beard and rinse well. They will need to be added before the shrimp. Turn heat to high and get soup to a rolling boil. Add mussels and half of the cilantro. cook for 3 to 4 minutes until they start to open. Then add shrimp. Return to a rolling boil. Then cover, turn off heat and let sit on burner 5 minutes before serving.

If using frozen mussels. They need to be thawed. Add mussels, shrimp, and half of the cilantro at the same time. Including the liquor the mussels are packaged in. Bring to a rolling boil. Shut off heat and cover for 5 minutes.

Serve with fresh cilantro garnish, and lime wedges if desired. Enjoy.