Cook 3/4 cup uncooked rice according to the package directions; keep warm.

Trim the ends from 12 ounces fresh green beans. Steam or boil the green beans until they reach your desired tenderness (about 3–6 minutes for tender-crisp). Drain and set aside.

Chop scallions to taste and set aside for garnish.

Place the 2 large chicken breasts (cut into bite-size pieces) and 3 tablespoons cornstarch into a large resealable bag or a bowl. Seal or cover and toss/shake until the chicken pieces are evenly coated with cornstarch. Shake off any large excess.

In a small bowl, whisk together 1/2 cup packed brown sugar, 3 cloves minced garlic, 1 teaspoon grated fresh ginger, 1 tablespoon soy sauce, 1 teaspoon sriracha sauce, and 1 cup water until smooth.

Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Add the cornstarch-coated chicken in a single layer as much as the pan allows (cook in batches if needed). Cook, stirring occasionally, about 4–6 minutes, until the chicken is no longer pink on the outside and beginning to brown.

Pour the prepared sauce into the skillet with the chicken and reduce the heat to medium. Stir to combine, then simmer 5–8 minutes, stirring occasionally, until the chicken is cooked through (internal temperature 165°F if using an instant-read thermometer) and the sauce has thickened to coat the chicken.

If you cooked the chicken in batches, return all chicken to the skillet and toss in the sauce to coat evenly. Taste and adjust by cooking a little longer if the sauce needs more thickening.

Divide the cooked rice, green beans, and saucy chicken evenly among your meal-prep containers. Garnish with chopped scallions. Reheat in the microwave before eating.