Separate the oyster mushrooms (if they're all connected in a bunch) into bite-sized pieces.
Place a bamboo steamer over a pan of simmering water or switch on an electric steamer. Fill with your bao buns, separated by greaseproof paper so the don't stick to the steamer or to eachother. Steam gently for around 20 minutes.
Meanwhile, place a medium, high-sided saucepan over a medium heat and fill with around 2 inches of vegetable oil. Bring to around 170c. If you don't have a thermometer, just drop a little bit of your spiced flour mixture in after a few minutes - it should sizzle and bubble immediately.
Once your oil is hot, with one hand take an oyster mushroom and roll it around in the spiced flour. Remove it from the flour with the same hand and drop into the "egg" mixture.
Use the other hand to remove the mushroom from the "egg" mixture and drop it back into the spiced flour. Cover it in flour with the same hand, then carefully drop it into the hot oil. Quickly repeat the process with another three mushrooms.
Fry the mushrooms in small batches until golden brown and crispy on the outside. Remove from the oil and place on a tray lined with kitchen roll, to help absorb some of the excess oil. Repeat until all the mushrooms are fried.
Whisk your buffalo sauce to re-homogenise. Place the fried oyster mushrooms in a bowl and then drizzle the sauce over them. Toss or gently stir to combine.
Fill each steamed bao bun with fried, dressed mushrooms and some sprigs of coriander. Enjoy!