Soak black Chinese mushrooms and lily buds in warm water for 30 minutes to rehydrate; drain thoroughly.

Thinly slice the rehydrated black Chinese mushrooms, discarding any tough stems.

If using lily buds, cut off and discard the hard tips. Tie each bud into a knot.

Cut bamboo shoots into matchstick-sized pieces.

Slice the boneless, skinless chicken breast into thin, uniform slices.

In a small bowl, mix the sliced chicken with dry sherry and let it marinate for 15 minutes.

In a separate small bowl, whisk together cornstarch and 3 tablespoons of water to create a slurry.

In a large pot or Dutch oven, bring chicken broth to a simmer.

Add the marinated chicken to the simmering broth and cook until it turns opaque, about 3-5 minutes.

Add the sliced mushrooms, knotted lily buds (if using), and bamboo shoots to the broth.

Stir in the cubed tofu and bring the soup back to a gentle simmer.

Slowly drizzle the cornstarch slurry into the soup while stirring constantly to thicken it to your desired consistency.

Season the soup with white pepper.

In a slow and steady stream, pour the lightly beaten egg into the simmering soup while stirring gently. This will create egg ribbons.

Stir in the white vinegar and sesame oil to achieve the desired sour and savory flavor balance.

Add soy sauce, adjusting the amount to taste.

Garnish with thinly sliced green onions and serve hot.