• Rinse the rice.

In a medium sauce pot, combine the rice and 2¼ cups water. Bring to a boil, reduce to a simmer, cover, and cook until the rice is tender and the liquid is absorbed, 15 to 20 minutes. Fluff with a fork, cover, and keep warm.
While the rice cooks, prepare the stir-fry.

• Remove the stem, ribs, and seeds from the bell pepper; cut the bell pepper into 1-inch pieces.
• Cut the broccoli into 1-inch florets; trim off any coarse stems.
• Trim the root ends from the scallions. Cut the white parts into 1-inch lengths for the stir-fry; thinly slice the green parts for garnish.

• Cut a small corner from the chicken packaging and drain off any excess liquid. Transfer to a medium bowl; pat dry with a paper towel. Season generously with salt and pepper. Add the arrowroot powder and stir to coat the chicken.

In a wok or large frying pan over medium-high heat, warm 2 to 3 teaspoons oil until hot but not smoking. Add the chicken and cook, stirring occasionally, until browned but not yet cooked through, 3 to 5 minutes. Transfer the chicken to a plate. Do not clean the pan.
While the chicken cooks, prepare the stir-fry sauce.

• In a small bowl, using a whisk or fork, mix together the stir-fry base and ¼ cup water.

In the same pan used for the chicken, if dry, add 2 to 3 teaspoons oil. Warm over medium-high heat until hot but not smoking. Stir in the bell pepper, broccoli, and white parts of the scallions and cook until crisp-tender, 1 to 2 minutes. Return the chicken and any accumulated juices to the pan and add the cashews and coconut vinegar. Cook, stirring occasionally, until the liquid evaporates, the vegetables are just tender, and the chicken is cooked through, 2 to 3 minutes. Stir in the stir-fry sauce and cook until thickened, 1 to 2 minutes. Remove from the heat and stir in the water chestnuts.

Transfer the rice to individual bowls. Top with the stir-fry, garnish with the green parts of the scallions, and serve.