Heat up the oil over high heat in a medium sized cooking pot and add the lemongrass, chili peppers, soy sauce, and fish sauce. Once fragrant, stir in the bột bò kho and reduce the heat to medium high. Then, add the fried tofu, mushrooms, carrots, onions and enough of the boiled water to cover about ¾ of the ingredients in the pot. Allow to simmer for about 12-15 minutes. If you prefer to have more of a crunch to the carrots and onions, you can add them in 3-4 minutes before the end of the cooking time. Finish by garnishing with finely chopped basil and culontro.