Trim ends from green onions and finely chop

Remove stems from shiitake mushrooms and thinly slice

Melt 2 tablespoons butter in a medium skillet over medium high heat

Add the green onion and toss to wilt, 1 minute

Add the mushrooms and cook for 3 to 5 minutes or until wilted and tender

Season to taste with salt and pepper

Cool completely. Wash and thoroughly dry the chicken breasts

Cut a pocket in the side of each breast about 2 inches long. Spoon the mushrooms into the chicken pockets and secure edges with toothpicks

Melt remaining 2 tablespoons butter in a large skillet over medium high heat

Add the chicken and brown well, about 3 minutes per side

Reduce heat to medium low and add the Teriyaki sauce to the pan

Cover and cook chicken until cooked through, about 8 to 10 minutes, turning chicken once to glaze both sides.