Heat the oil in a large soup pot over high heat. Add the shallot, garlic, and ginger, cut side down and cook without moving for 3–4 minutes until the aromatics begin to char. Add the lemongrass and scallions and cook another minute or two.

Pour in the water and bring to a boil.

Place a small skillet on the stovetop over high heat. Add the cinnamon, cloves, star anise, and black peppercorns and cook, swirling the spices in the skillet for 1–2 minutes until very fragrant. Pour the hot spices directly into the boiling water and wipe out the skillet (you will need it for the mushrooms later on).

Add the sugar and salt to the broth. Reduce the broth to low and simmer for 45 minutes.

After the broth has simmered, turn off the heat. Place a sieve over a large bowl and pour the broth into the sieve. Discard the solids. Wipe out the pot and return it to the stovetop.

Heat 1 tablespoon neutral oil in the soup pot over medium-high heat. Add the sliced onion and cook for 6–7 minutes. Add the 12 ounces mushrooms and cook, stirring occasionally, for 12–15 minutes—season with salt to taste.

Pour in the reserved stock and bring it to a boil. Reduce heat to low and simmer as you finish the rest of the soup ingredients.

Bring a large pot of water to a boil and cook the rice noodles according to package instructions. Drain, rinse and divide between four bowls.

In the skillet used to toast the spices, heat another tablespoon of neutral oil. Add the mushrooms and cook without moving for 3–4 minutes or until golden brown. Flip and cook an additional 3–4 minutes. Season with salt and turn off the heat.

Ladle the hot broth over the noodles in each bowl. Pile the crispy oyster mushrooms on top and garnish them with Thai basil, scallions, jalapeño, and any desired garnish. Enjoy!