Preheat your air fryer on the bake function to 180°C.
Slice the king oyster mushrooms lengthwise into strips approximately ½ cm thick. Add them to the preheated air fryer with 1 tsp oil and toss to coat. Bake for 10 minutes, shaking occasionally to ensure they sear evenly.
Meanwhile, mix all the dressing ingredients in a bowl.
Remove the mushrooms from the air fryer and toss them in the dressing until evenly coated. Return the mushrooms to the air fryer for a final 5 minutes, shaking once midway to ensure even caramelisation.
Remove the mushrooms from the air fryer. Taste and adjust seasoning if needed. The strong flavour will balance out the juiciness of the tomato and lettuce in the sandwich.
Slice the tomatoes, wash and rinse the lettuce, and toast the bread if desired.
Spread vegan mayo on one side of each slice of bread. On two slices, layer the tomatoes, lettuce, and mushrooms. Top with the remaining slices of bread, mayo side down.
Serve and enjoy!