Clean and trim the lion's mane mushrooms, removing any tough stems. Break apart the mushrooms into small, sizeable chunks.
In a bowl, combine all ingredients for the batter - flour, corn starch, spices, salt and black pepper. Mix together with whisk.
Add oat milk slowly to the batter until you get a thick and smooth batter (not too thick and not runny).
Heat oil in a pan and make sure there's enough oil for the mushrooms to be fully submerged.
Coat the mushrooms in the batter and carefully place into oil. The oil must immediately start sizzling.
Keep a close eye and fry mushrooms until golden brown. As you're frying all the mushrooms, you can start on the sauce.
To a separate pan, add sesame oil and heat up. Add the white part of scallions and saute.
Then add sliced garlic and minced ginger. Saute until aromatic.
Add gochujang, ketchup, rice wine vinegar, soy sauce and maple syrup. Add a splash of water to loosen the sauce.
Add the fried mushrooms back in and serve immediately with toasted sesame seeds and scallions. Enjoy!