Soy sauce, cilantro leaves and sliced hot chiles, for serving
In a large bowl, whisk the flour with the cornstarch, salt, peppercorns and five-spice powder. Lightly whisk in the seltzer—the batter should be a little lumpy.
In a large saucepan, heat the vegetable oil to 375°. Meanwhile, set a wire rack over a baking sheet. Working in 5 batches, add the squid to the batter: Lift each piece from the batter, drag it against the side of the bowl to remove any excess and drop it gently into the hot oil. Use a frying screen to prevent oil from splattering. Continue adding the squid to different parts of the saucepan until the whole batch has been added. Fry the squid over high heat until deep golden, about 2 minutes. Using a slotted spoon, transfer the squid to the rack. Repeat with the remaining 4 batches of squid. Serve the squid at once with the soy sauce, cilantro and chiles.