If frying, preheat oil in a dutch oven on your stovetop, or in a countertop deep fryer to 375°F (190°C). If air frying, preheat the air fryer to 375°F (190°C). Lightly coat the air fryer basket with oil.
Cut or hand-tear the seitan into natural, 3-4 bite size portions.
Prepare a dredging station. In one bowl, add the flour. In a second bowl, whisk the plant-based milk and sriracha, then let it sit for a few minutes to curdle. In a third bowl, mix the potato starch, gochugaru, and salt.
Dredge each piece in the flour, then dip into the curdled milk, ensuring full coverage before dripping off back into the bowl. Finally, coat in the potato starch mixture, pressing gently to adhere. Place the coated pieces on a tray.
Either fry for 2-3 minutes on each side in batches, or air fry for 8-10 minutes, flipping halfway through, until crisp and golden brown.
To prepare the sauce, combine the tomato paste, gochujang, maple syrup, tamari, sesame oil, garlic, and ginger in a saucepan. Cook over medium heat, stirring frequently, until slightly thickened.
Toss the fried (or air-fried) seitan in the sauce until evenly coated.
Optionally, roast the coated seitan for 10-12 minutes on a parchment paper-lined baking pan at 350 degrees to caramelize the sauce onto the wings, so they set up nice and crispy.
Transfer to a serving dish and garnish with black sesame seeds, toasted sesame seeds, and sliced scallions. Serve immediately with radish kimchi.