Cut the chicken breast and enoki mushrooms into bite-sized pieces, and slice the onion thinly.
Heat cooking oil in a pan and stir-fry the chicken breast.
When the chicken breast is about halfway cooked, add the onion and enoki mushrooms and stir-fry together.
Season with soy sauce, mirin, and minced garlic.
Once all the ingredients are cooked through, place them over rice to complete the rice bowl.