Make the marinade: Add all the marinade ingredients to a measuring glass. Stir and taste - adjust any flavors if necessary! Pour the marinade and chopped chicken into a bowl or zip-top bag and let it sit for at least 15 minutes, up to 2 hours.
For the rice: add the rice, water, coconut milk, and salt to a pot and stir once. Bring it to boil, then cover and turn the heat all the way down (but not off). Cook for 10 minutes, then turn off the heat and steam for 10 minutes.
Cook the chicken: Add 1 TBSP oil to a skillet (I used cast iron) over a medium flame. Let it heat up for a few minutes, then add the chicken to the pan. Make sure to space the chicken out a little and avoid getting the marinade in the pan (otherwise the chicken will just boil). Cook on each side for 5 minutes, then remove it from the pan and set aside.
Cook the veggies: To the same skillet, add a little more oil, followed by the chopped veggies, white ends of the scallions, garlic and soy sauce. You may need to cook the veggies in batches depending on the size of your pan. Cook over medium/high heat for about 7-10 minutes, stirring often, until the veggies are fork-tender.
Make the peanut sauce (optional): Add the peanut sauce ingredients to a measuring glass and whisk well with a fork. Add water to thin (I added about 3 TBSP) to your desired consistency. Taste and adjust flavors as necessary.
Assemble: Divide the rice, veggies and cooked chicken between three meal prep containers. Divide the sauce between three smaller containers or just keep it in one bigger container on the side to drizzle on before eating. Garnish with chopped green ends of the scallions.