Step 1

Preheat an air fryer to 390 degrees F (200 degrees C).

Step 2

Place oyster mushrooms in a bowl and pour buttermilk on top. Toss to coat mushrooms with buttermilk and marinate for 15 minutes.

Step 3

Meanwhile, add flour, salt, pepper, garlic powder, onion powder, paprika, and ground mustard to a large resealable zip-top bag. Seal and shake until evenly combined.

Step 4

One at a time, take a mushroom out of the buttermilk mixture and drop in the seasoned flour. Toss to coat and transfer to a plate. Once all mushrooms are coated, repeat the breading step until all mushrooms are breaded twice and set them on another plate.

Step 5

Spray the basket of the air fryer with nonstick cooking spray. Spread out breaded mushrooms in the basket of the air fryer in one layer, making sure not to overcrowd (you will need to do this in batches).

Step 6

Air-fry mushrooms for 4 minutes. Liberally brush mushrooms with vegetable oil and air-fry for 4 minutes more. Using tongs, flip the mushrooms over and cook 2 minutes more. Repeat with remaining mushrooms