Fill a pot with 2 quarts of water and set it to high heat.
Once it reaches a boil, add the bouillon paste or powder and whisk to combine.
Reduce the heat to medium-high and gently add the tofu cubes.
Cover and cook for 5 minutes.
Uncover and continue to simmer for an additional 2 to 3 minutes.
Using a slotted spoon, carefully remove the tofu from the pot and transfer it to a towel-lined plate to drain and cool.
Place the cornstarch and kosher salt in a large bowl and mix to combine. Set aside.
Place the garlic salt, black pepper, and white pepper in separate bowl and mix to combine. Set aside.
Meanwhile, heat the vegetable oil in a wok or large sauté pan over medium heat.
Transfer the tofu to the bowl with the cornstarch and toss gently to combine, ensuring all the tofu pieces are coated with cornstarch. You may need to do this in batches.
Once the oil is hot, fry the tofu in batches until crispy and light golden-brown, 5 to 8 minutes, stirring every so often to ensure even frying.
Using a slotted spoon, transfer the crispy tofu pieces to a paper towel lined plate and repeat until all the tofu pieces are fried.
Remove all but 2 tablespoons of the vegetable oil from the wok you fried the tofu in.
Heat the oil over medium heat.
Once the oil is hot, stir fry the white onion, white and light green parts of the green onion, garlic, and Thai chilies until fragrant, 2 to 3 minutes.
Toss in the fried tofu, season with the garlic salt and pepper mixture, and continue to stir-fry until coated in the seasoning and heated through 3 to 4 minutes.
Garnish with thinly sliced green onion and serve immediately. ENJOY!