Bruise the lemongrass stalks by pressing on them with a large knife, until they flatten a bit. Cut each stalk into 4 sections. Set aside.
Heat 2 teaspoons of oil in medium saucepan over medium heat. Add the garlic and ginger. Sauté for 1 minute.
Add the broth, lemongrass, chili paste, shiitakes and cherry tomatoes. Bring everything to a low simmer and allow to cook about 12-15 minutes, until the mushrooms are tender.
While broth simmers, cut the tofu into ½ inch cubes. Coat a medium skillet with remaining 1 teaspoon of oil and place it over medium-high heat. Arrange the tofu cubes in a single layer. Cook about 5 minutes, until lightly browned on bottoms, turn and cook another 5 minutes.
Add the tofu to broth mixture, along with cilantro and lime juice, then give everything a stir.
Season with soy sauce to taste. Remove the lemongrass pieces and discard. Ladle the into bowls and serve.
