Heat the Oil: In a large skillet or wok, heat vegetable oil over medium-high heat.
Sauté Aromatics: Add garlic and ginger, stir-frying for 30 seconds until fragrant.
Cook the Mushrooms: Toss in the sliced mushrooms and cook for 3-4 minutes until they start to soften.
Add Bok Choy: Stir in the bok choy and cook for another 2-3 minutes until tender but still crisp.
Make the Sauce: In a small bowl, mix soy sauce, oyster sauce, sesame oil, red pepper flakes (if using), water, and cornstarch. Pour over the vegetables and stir well.
Simmer & Serve: Let the sauce thicken for 1-2 minutes, then remove from heat. Garnish with sesame seeds and serve hot!