Step 1 (Prep Ingredients: Soak dried mushrooms in hot water for 20 minutes until softened. Squeeze dry, discard stems, and thinly slice. Slice all other ingredients into uniform thin strips (julienne) for even cooking. Have cornstarch slurry ready.
Step 2 (Cook Protein & Mushrooms: Bring 6 cups broth to boil in large pot. Add julienned pork/chicken, sliced mushrooms, and bamboo shoots. Simmer for 5 minutes until meat is cooked through.
Step 3 (Season Broth: Add 2 tbsp soy sauce, 1 tsp dark soy sauce (for color), 1 tsp freshly ground white pepper (critical for authentic heat), and salt to taste. Add tofu strips. Simmer for 3 minutes.
Step 4 (Thicken Soup: Give cornstarch slurry a good stir. While soup is at a gentle boil, slowly drizzle in slurry while stirring constantly. Cook for 2-3 minutes until soup thickens to a velvety consistency that coats the back of a spoon.
Step 5 (Add Vinegar & Egg: Turn off heat. Immediately stir in 3 tbsp rice vinegar (adding at high heat preserves sharpness). Wait 10 seconds, then slowly drizzle beaten egg in a thin stream while stirring gently in one direction – this creates silky ribbons. Let sit for 30 seconds to set.
Step 6 (Finish: Stir in 1 tsp sesame oil. Taste and adjust seasoning; it should be boldly sour and peppery. Add extra 1/2 tsp white pepper powder if desired.
Step 7 (Serve & Store: Ladle into bowls immediately. Garnish with chopped green onions and cilantro. Soup can be refrigerated for 3 days but will thicken when cold. Reheat gently with added broth or water to adjust consistency. Freeze without egg for up to 1 month; add fresh egg when reheating.
