In a large pot, add 4 cups of water or chicken broth. Bring it to a gentle simmer over medium heat. Once simmering, add the bruised lemongrass, galangal slices, and torn kaffir lime leaves. Let these ingredients infuse the broth for about 10 minutes to release their aromatic flavors.

Pour in the 2 cans of coconut milk, stirring gently to combine. The creamy coconut milk is what gives Tom Kha its rich, velvety texture. Stir occasionally as the broth continues to simmer, allowing the flavors to meld together.

Add your protein of choice (chicken, shrimp, or tofu) to the pot. If you're using chicken, ensure it's cut into bite-sized pieces for even cooking. Let the protein simmer for about 5-7 minutes or until fully cooked through.

Add 3 tablespoons of fish sauce and 2 tablespoons of fresh lime juice. This combination brings the essential salty, umami, and tangy elements that make Tom Kha so irresistible. Adjust the seasoning as needed, tasting along the way to ensure the perfect balance of flavors.

Stir in 1 cup of sliced mushrooms and 2 chopped tomatoes (optional). Let the mushrooms cook for 3-4 minutes until tender, soaking up the broth’s delicious flavors.

Add 2-3 Thai bird's eye chilies, or adjust to your heat preference. If you prefer a milder soup, remove the seeds from the chilies before adding them.

Let the soup simmer for another 5-7 minutes to allow all the ingredients to meld together. Taste the soup and adjust the lime juice, fish sauce, or sugar as needed. If you prefer a sweeter note, add a teaspoon of sugar to balance the acidity.

Once the soup is ready, ladle it into bowls and garnish it with fresh chopped cilantro for a burst of color and flavor. Serve with steamed jasmine rice, or enjoy it on its own for a light and flavorful meal.