Use mushroom of your choice . Simply quarter them if they are big.
Use chilly sauce of your choice . I have used siracha
Use toasted bread crumbs or mix of fresh bread crumbs and raw/semolina to substitute panko
Substitute flaxseed meal slurry with equal mix of corn starch and all purpose flour/ maida slurry. 2 tablespoon each with some water to form a thin coating batter.
Spice level of this recipe is 4 on 5 , 5 being hot.
Adjust spice accordingly