Wash the mushroom by immersing them in a bowl of water. Remove the black dirt and clean them with fresh water. Later wipe it off with a kitchen towel.
With the head part facing down, cut each mushroom into 3-5 thin pieces depending on the size of the mushroom.
Whisk soy sauce and vinegar in a small bowl and set aside.
Heat oil in a wok over high heat.
Add chopped garlic and sliced onions into it and sauté for few minutes.
Next add sliced red bell peppers and stir constantly for 3-4 minutes.
After that add sliced mushrooms and keep on stirring for another 4-5 minutes.
Season the vegetables with salts and combine them.
Pour the sauce mixture over the vegetables and quickly toss them.
Finally, add freshly ground black pepper and sesame seeds on top and switch off the gas.