Heat a large skillet over medium heat. Add 2 tbsp of oil and swirl to coat the pan. When the oil shimmers, add the shiitake mushrooms and saute, stirring, until soft, about 6 minutes. Season with the salt to taste, remove, and set aside.

Return the same skillet to the stove over medium heat. Add the remaining 2 tbsp of oil and swirl to coat the pan. When the oil shimmers, add the ginger, onion, chiles, and lemongrass and saute, stirring occasionally, until soft, about 6 minutes.

Stir in the fish sauce, then add the chicken stock, lime leaves, and star anise. Cook over medium heat until the liquid is reduced by one-fourth, about 20 minutes. Strain, return to the skillet, and add the reserved shiitakes, the enoki mushrooms, vinegar, basil and white pepper. Taste and correct seasonings. Keep hot.

NOTES : * I did not have thai bird chiles so I used dried arbol chiles.

The original recipe called for making shrimp toast to serve with the soup. I omitted the shrimp toast and just served the soup as is.