Step 1

Prep lemongrass: Trim 1-inch (2.5 cm) off both ends of lemongrass stalk, and discard. Use the back of your knife to pound each stalk (this helps release the oils). Cut each stalk into about 3-inch (7 cm) lengths, then cut each piece in half lengthwise.

Step 2

Sauté aromatics: Heat oil in a large pot over medium-high heat. Add lemongrass and sauté, until fragrant, about 3 minutes. Add onion, sauté until golden at the edges, about 5 minutes. Add garlic and galangal, sauté, stirring constantly (so garlic doesn't burn), until fragrant, about 1 minute.

Step 3

Simmer: Add vegetable broth, chili, and lime leaves. Cover with a lid and bring to a boil. Reduce heat to medium low, simmer to let the flavors infuse, 20 to 25 minutes.

Step 4

Make zucchini noodles: Meanwhile, use a spiralizer to make zucchini "noodles".

Step 5

Finish soup: Use tongs or a slotted spoon to remove lemongrass from soup. Add tomatoes and mushrooms. Simmer uncovered until the mushrooms have softened, about 5 minutes. Add lime juice, tamari, sugar and coconut milk. Stir to mix well. Taste and add Sriracha (about 1 tablespoon but adjust to taste) and more lime juice (if needed).

Step 6

Serve: Pile zucchini noodles into bowls and ladle soup on top. Garnish if you'd like (see note 4).