Add the "meat", dry seasonings, soy sauce and feta to a bowl. Use your hands to mix it to combine. Split into 6 equal pieces. Roll each piece into a ball and flatten into a patty.
Spray some oil in a skillet over medium-high heat. Add the patties and cook until browned on both sides (approx. 3 minutes per side).
Meanwhile, toast the buns in the air fryer, oven or toaster. Combine the mayo and Calabrian chili paste in a bowl and mix to combine. Set aside.
To assemble spread a layer of the mayo on the bottom of each bun. Top with a patty, pickled onions and arugula.