Turn on the Instant Pot and select sauté High. Once it displays HOT, add oil. Once Oil is warm, add onions, mushrooms and bok-choy. Sauté on high heat until mushrooms release water and appear darkened. Flip the bok-choy so both sides char nicely. Cancel Sauté and remove the content from the pan. Keep it aside.
Turn on the Instant Pot and select sauté High. Once it displays HOT, add oil, celery, bay leaves, garlic and ginger. Sauté them stirring very frequently, until they have softened and released their aroma (about 3 minutes). Cancel SAUTE.
Now, add in the turmeric and ground black pepper. Stir the whole time as ground spices burn easily. Add about 4 cups of water or vegetable stock. Close the lid and select Manual ( Pressure Cook button on newer models) 5 minutes ( Vent Sealed) .
Once Instant Pot does cooking and beeps when done, wait for 10 minute on keep warm setting and release the remaining the pressure. Open the lid. The warming broth is ready.
Stir in cooked bok-choy, mushrooms and rice noodles. Season with salt and lime juice. Using a ladle, pour a cupful in each serving bowl. Garnish with fresh cilantro, chili flakes and ground black pepper. Enjoy your beautiful creation !!