Toss the chicken in 1 TBSP of cornstarch in a bowl or zip top bag. Set aside.
To a small bowl, add the sriracha, soy sauce, sugar, water and rice vinegar. Whisk well and taste it - adjust the sauce as needed (add more sugar to make it less spicy, add more sriracha to make it spicier) and set aside. In a separate small bowl, mix 1 TBSP water and cornstarch and set aside.
Add 1 TBSP oil to a skillet over medium heat, followed by the garlic and ginger. After a minute, add the frozen veggies with salt and pepper to taste and cook uncovered until heated through, stirring occasionally - about 7-10 minutes (depending on how long they've been out of the freezer). Then remove the veggies from the pan and set them aside.
Add 1 TBSP olive oil to the same skillet over medium heat. Then add the chicken. Add salt and pepper to taste and cook on each side for about 5-7 minutes, until the edges of the chicken look crispy. Flip once or twice. When finished, turn off the heat, but keep the chicken in the pan for now.
While the chicken cooks, cook the rice according to the package.
Last but not least, the sauce. Pour the soy sauce and sriracha mixture in a small saucepan over medium heat and cook until it reaches a gentle boil. Give the cornstarch and water a quick stir, then slowly add it to the saucepan while whisking. Cook until the sauce has thickened (about a minute) Then, turn off the heat and pour it over the cooked chicken/tofu and toss the pieces to coat them in the sauce.
Assemble: Divide the cooked rice between three meal prep containers, followed by the veggies. (I mixed my rice and veggies together). Then add the chicken on top. Garnish with sesame seeds and green onion if desired.