Begin by slicing the chicken breast into thin, bite-sized strips. Rinse and slice the red and green bell peppers into thin strips as well. Mince the garlic finely, and pluck the fresh Thai basil leaves from their stems. Having all your ingredients ready before you start cooking will make the stir-fry process smooth and quick.
In a small bowl, combine the soy sauce, oyster sauce, sugar, ground black pepper, and crushed red pepper flakes. Stir until the sugar dissolves. This sauce will bring the perfect balance of salty, sweet, and spicy to the dish.
Heat the vegetable oil in a large skillet or wok over medium-high heat. When the oil shimmers, add the sliced chicken in a single layer. Let it sear without moving for about 1-2 minutes, then stir-fry until the chicken is cooked through and lightly golden, about 4-5 minutes total. Remove the chicken from the pan and set aside.
In the same pan, add a touch more oil if needed, then toss in the minced garlic. Stir quickly for about 30 seconds until fragrant but not browned. Add the sliced red and green bell peppers and stir-fry for 2-3 minutes until they start to soften but remain crisp and vibrant.
Return the cooked chicken to the skillet with the peppers. Pour the sauce over everything and toss well to coat. Cook for another 1-2 minutes to let the flavors meld. Finally, remove from heat and fold in the fresh Thai basil leaves, letting their aroma infuse the dish without cooking them too long.
Spoon the Thai Basil Chicken Stir-Fry with Peppers over bowls of fluffy jasmine rice. The rice soaks up the sauce perfectly, making every bite a delight.