In a bowl, whisk together the soy sauce, cornstarch, mirin, and sesame oil. Add in the chicken, and let it sit for 20-30 minutes.
1/4 cup soy sauce, 2 tablespoons cornstarch, 1 tablespoon mirin, 1 teaspoon sesame oil, 1 1/2 pounds chicken breast*
Heat the vegetable oil in a large skillet over medium high heat. Once heated, add in the chicken pieces, and cook for 2-3 minutes per side until cooked through. Place the cooked chicken on a plate.
3 tablespoons vegetable oil
Make sure all veggies are dry before adding them to the wok to avoid steaming instead of stir-frying. Add the onion, bell peppers, and Thai chilis to the same skillet, and cook for a few minutes until browned and softened. Add in the garlic and cook for another minute.
1/2 onion, 1 green bell pepper**, 1 red bell pepper, 10-15 dried Thai red chilis, 3 cloves garlic
Add the chicken back to the skillet along with the peanuts, and toss with the vegetables.
1/3 cup peanuts
Pour in the Szechuan sauce and stir to combine. Cook for another 1-2 minutes until the sauce thickens.
1 batch of homemade Szechuan sauce
Sprinkle with chopped green onion, and serve with rice.
Chopped green onion