Soak the shiitake mushrooms in boiling hot water for 30 minutes (make sure to fully submerge in water). Once complete; rinse, squeeze and clean the mushrooms at least 2 times. Cut and remove the stems.
Clean and rinse the bok choy. Remove the bottom tips and slice in half (lengthwise).
In a wok/pan: Boil 2 cups of water. Add bok choy, place the lid on and blanch/steam for 1-2 minutes. Drain the bok choy in a strainer. Set aside.
Using the same wok/pan: Add 2 tbsp oil and shiitake mushrooms.
Then add soy sauce, oyster sauce, sesame oil, dark soy sauce, water, broth and mix. Cook for 3-4 minutes.
Pour in cornstarch mixture (½ tbsp + 2 tbsp water). Cook for 3 minutes. Stir frequently until the sauce thickens.
Season with salt to taste.