Thoroughly wash mushrooms and cut them in half. Cut spring onion into finger-length pieces.
Place a large frying pan on medium heat. Put cooking oil (~3T) into the pan. Once the oil is hot, place in the minced garlic (2T).
Once the garlic starts to sizzle, place in the mushrooms. Stir the mushrooms around for 1 minute (careful not to burn the minced garlic).
Once most of the oil in the frying pan has evaporated, place in the water (1.5 cups).
Raise the heat to a medium-high. Then place in the soy sauce (2T), sugar (1t), oyster sauce (1T) and black pepper (few shakes).
Once the sauce comes to boil, lower the heat back to a medium. Then let it simmer away for 4-5 minutes.
In the meanwhile, make the thickener: Mix cornstarch (2T) with water (2T).
Place in about 1/2 of the corn starch mixture to thicken the sauce (Place in more if you need).
Throw in the spring onion pieces. Turn off heat.
Add sesame oil (1T). Add a few shakes of salt to taste.
Serve with rice. Bon Appetit!