Finely chop the garlic and cut the tofu into large, bite-sized cubes. Add oil to the pan and set the temperature to high. Add in the garlic and stir. When the garlic just begins to turn a light brown, add in the pork and stir. Try to break down the pork as much as possible.
Add in shoyu when the pork is half brown, half red. Continue to stir to allow the pork fat to cook the shoyu. Adjust the heat between medium to medium-high.
Add all of the tofu to the pan when the overall color of the pork turns brown.
Add water and stir gently to mix the water with all of the meat juices. Adjust temperature to high heat. Add sriracha, salt, pepper, brown sugar, and shoyu. Stir everything together until it is fully mixed.. Cover the pan with the lid and leave it slightly open to let the steam out. When it begins to boil lower the heat to medium-low. Cook for another 8 - 10 minutes and stir every few minutes.
Prepare the cornstarch and water mix. You can prepare this earlier, but make sure you mix it before you pour it into the pan as the cornstarch sinks to the bottom over time.
Remove the lid and slowly pour in half of the cornstarch-water mixture. Stir. Repeat with the remaining cornstarch-water mixture. Let this cook for another few minutes so that the cornstarch cooks completely. The juices should slightly thicken like a light gravy. As this cools, this will become even thicker.
Turn off the stove and add in the green onions. Add in sesame seed oil and stir.