In a small bowl, whisk together the chicken broth, soy sauce, oyster sauce, and cornstarch until smooth; set aside.
Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat.
Add the chicken pieces and cook until browned and cooked through, approximately 5 to 7 minutes, then remove from the skillet and set aside.
Add the remaining 1 tablespoon of oil to the skillet and sauté the mushrooms until they have released their moisture and turned golden brown.
Stir in the minced garlic and grated ginger, cooking for 30 seconds until fragrant.
Return the cooked chicken to the skillet and pour the prepared sauce mixture over the ingredients.
Toss constantly for 1 to 2 minutes until the sauce has thickened and coats the chicken and mushrooms evenly.
Remove from heat, stir in the sesame oil, and garnish with sliced green onions before serving.