Soak the Dry rice vermicelli (bún) in warm water for 10–15 minutes or until pliable, then drain and set aside.
Prepare the seafood and proteins: rinse and devein the Large shrimp, clean and score the Squid, cut the Firm white fish fillet into large pieces, and scrub the Mussels; cut the Fried tofu puffs into bite-sized pieces.
Prep aromatics and produce: smash and trim the Lemongrass and slice the Galangal thinly; tear a few Kaffir lime leaves; halve the Onion and roughly chop the Tomatoes and Pineapple; mince the Garlic and slice a few Bird's-eye chilies for heat.
Make the broth: bring the Chicken stock to a gentle simmer in a large pot and add the lemongrass, galangal, kaffir lime leaves, onion, garlic, tomatoes and pineapple. Simmer gently for 15–20 minutes so the aromatics infuse the broth.
Season the broth: stir in the Tamarind pulp for tang, add Fish sauce to taste, dissolve a small piece of Rock sugar to round the flavors, and whisk in a spoonful of Sa tế (Vietnamese chili satay) for depth and color. Taste and adjust acidity, salt and sweetness—add a little lime juice or more fish sauce if needed.
Add the heartier seafood and vegetables: first add the mussels and cook until they begin to open, then add the fish pieces and cook 3–4 minutes, followed by the shrimp and squid—cook just until opaque. Add Straw mushrooms, shredded Napa cabbage and pieces of Water spinach (morning glory) and simmer briefly until the greens are tender-crisp.
Finish and balance: stir in the Fried tofu puffs so they soak up some broth, and adjust seasoning with more fish sauce or a pinch of sugar if needed. Remove from heat and toss in torn Rice paddy herb (ngò om), sliced Sawtooth coriander (ngò gai) and chopped Cilantro for a bright, herbal finish. Squeeze fresh Limes over the pot just before serving.
Serve family-style: arrange bowls with softened vermicelli and ladle the hot broth, seafood and vegetables over the noodles. Offer extra Fish sauce, sliced Bird's-eye chilies and wedges of Limes at the table for guests to customize their bowls. Enjoy immediately while steaming hot.
