Fry rice noodles until they puff up and float to the top, then flip and remove to a paper towel.
Put clams in a pan with Broth and bring to a simmer. Cover until clams just start to open. Add mussels, scallops and prawns, then cover to steam.
Bring oil to 375 degrees F in deep-fryer.
Coat crab in potato starch and fry until crispy and 80 percent cooked through; remove to a bowl. Add cherry tomatoes and scallions, then toss. Add rice noodles to a bowl, then arrange softshell crab and its sauce over noodles. Finish sauce with Sweet Chili Paste. Taste broth, place crab in center and pour over seasoned pan broth. Garnish with micro herbs.
Thom Ka Steamer Broth:
Bring coconut milk to a simmer in a pot. Bruise and slice lemongrass, then add to a sachet along with galangal and chiles; drop into liquid. Add sugar, fish sauce, salt, lime leaves, lime juice and 1 quart water, then cover, turn off the heat and let steep for at least 2 hours Let cool, then refrigerate. Remove sachet before using.
Sweet Chili Paste (Nam Phrik Pow):
Crush chiles in a mortar until they turn into a powder and reserve. Smash shallots and garlic into a paste and reserve. Crush dried shrimp into a powder and reserve. Crush cilantro and galangal into a paste and reserve.
Heat half the oil in a wok or pan over high heat, then add, in this order and cooking for 20 seconds or so between each addition: Chiles; shallots and garlic; dried shrimp; and cilantro/galangal paste. Season with tamarind, sugar, fish sauce, salt and shrimp paste. Add remaining oil and simmer, stirring often, 1 minute more. Season to taste. Finish with lime juice. Cool and refrigerate. Paste keeps, refrigerated, for weeks.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.