Mix tamari and vinegar in a bowl until well combined.
Add the tofu cubes and let rest for at least 5 minutes.
Drain the tofu and transfer 1/3 of the tofu cubes to a freezer bag with 2 tbsp of cornstarch and toss to coat. Repeat this step with the rest of the tofu and cornstarch. Add more cornstarch if needed.
Cook the tofu cubes in a skillet with a little bit of oil over medium-high heat until all sides are golden brown. Remove tofu from pan and set aside.
Add the garlic to the skillet and cook them over medium-high heat for about 1 to 2 minutes, stirring frequently until they start to golden brown.
To make the sauce just mix all the ingredients until well combined.
Add the sauce to the skillet and cook until it thickens, stirring frequently.
Finally, add the tofu, stir and cook for 1 to 2 minutes more.
Remove pan from heat and serve with some white rice and garnish with sesame seeds and chopped chives (optional).
Keep leftovers in a sealed container in the fridge for up to 5 days.