Make the homemade teriyaki marinade by putting all of the marinade ingredients in a small saucepan. (1/2 cup cold water, 1/3 cup brown sugar, 1/4 cup soy sauce, 2 tbsp vinegar, 1 tbsp sesame oil, minced garlic, ginger root, garlic chili paste, and 1 tbsp corn starch) and simmer over medium heat until all of the sugar dissolves.
Drain and press your extra firm tofu to get as much excess water out of it as possible.
Cut the tofu into 1/2 inch cubes.
Marinate the tofu in the teriyaki marinade for at least 15 minutes. (The teriyaki marinade is the same as the homemade sauce, but without the starch to thicken it. This way your tofu will be able to soak up the sauce.)
Pour the marinade back into a saucepan. Mix 1 tablespoon cornstarch with 2 tablespoons of water and stir it into the marinade. Turn on the heat and bring to a boil while stirring frequently to thicken the sauce.
Stir fry the tofu in 1 tbsp of sesame oil on medium-high heat, flipping frequently until the tofu cubes become crispy on all sides.
While the tofu is cooking, wash and cut about 3 cups of any veggies that you want to add to the dish.
Remove the cooked tofu from the skillet, and add an additional tablespoon of sesame oil.
Stir fry the veggies for about 3-5 minutes over medium-high heat until they are cooked, but not mushy.
Add the tofu back into the skillet with the veggies and drizzle with about 1 cup of thickened teriyaki sauce.
Mix well and serve over rice or noodles.
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Notes
Make sure to drain and press your tofu well.
Add the teriyaki sauce after cooking to prevent it from sticking and burning.
Marinate the tofu for at least 15 minutes. You can marinate it a day or two in advance, but be sure to keep it refrigerated until ready to cook.