Prepare Ingredients: Wash and pat dry chicken thighs. Cut into uniform chunks. Drain tofu and cut into equal-sized cubes. Mince garlic, slice the onion, julienne ginger, and chop green onions.
Brown the Chicken: Heat vegetable oil in a large skillet over high heat. Add chicken pieces and sauté until browned on all sides.
4 each chicken thighs, boneless and skinless, 2 tbsp vegetable oil
Sauté Aromatics: Add minced garlic, sliced onion, julienned ginger, and half of the chopped green onions to the skillet. Sauté until fragrant, approximately 1-2 minutes.
6 cloves garlic, 2 inches ginger, 4 each green onion, 1 each onion
Deglaze and Simmer: Pour in water, soy sauce, and Mirin to the skillet, stirring to deglaze the pan. Bring the mixture to a simmer.
1/4 cup soy sauce, 1/4 cup water, 2 tbsp mirin
Add Tofu: Gently fold in tofu cubes, being careful not to break them. Cover and let simmer for 10-15 minutes, allowing flavors to meld and chicken to cook thoroughly.
1 block medium-firm tofu
Reduce Sauce: Remove the lid, increase heat to medium-high, and allow the sauce to reduce to the desired consistency. For a thinner sauce, reduce briefly. For a thicker sauce, continue reducing until it coats the back of a spoon.
Final Garnish and Serve: Remove from heat. Garnish with remaining green onions. Serve hot, ideal with a side of steamed rice.