Begin by heating a tablespoon of oil in a heavy-bottomed pot over medium heat. Add the diced onion, quartered mushrooms, and chopped bok choy, cooking for about 5-7 minutes until the onions turn translucent and the mushrooms are nicely browned.

In the same pot, add the finely chopped celery, bay leaves, minced garlic, and grated ginger. Cook these ingredients over low heat for approximately 3 minutes until they become fragrant.

Next, stir in the turmeric powder and ground black pepper, cooking for an additional 30 seconds while keeping the heat low.

Pour in 4 cups of low sodium vegetable stock or water into the pot, raising the heat to bring the mixture to a boil. Once boiling, reduce the heat and let it simmer uncovered for about 20 minutes.

After simmering, add salt and a tablespoon of lime or lemon juice. Serve the broth over warmed thin rice noodles in individual bowls, then top with the sautéed bok choy and mushrooms. Garnish with fresh cilantro and sprinkle with optional chili flakes.