Cut the squid tubes into ¾-inch rings and halve large tentacles. For bigger squid bodies, slice open and score in a criss-cross pattern and cut into uniform sizes.
Soak the squid in a mixture of a cup of milk with a teaspoon of kosher salt (use half for table salt). Cover and refrigerate for about one hour.
Combine all-purpose flour, potato flour, and baking powder in a separate bowl. Drain the squid and coat them, shaking off any excess flour.
In a saucepan or wok, heat about an inch of oil over high heat. To test if the oil is hot enough, insert the handle of a wooden spoon or a chopstick. If it's ready, you'll see steady bubbling around it. If you have a cooking thermometer, the oil should be at 375° F (190° C).PRO TIP: Make sure the oil is very hot before dropping in the squid. This high temperature allows the squid to brown and crisp quickly, preventing overcooking.
Fry in batches until they turn golden brown, about 2 minutes. Gently stir them to prevent sticking together. Don't overcrowd them when frying to avoid a temperature drop which can make them greasy and soggy.PRO TIP: Remember to bring the oil back to a high temperature between each batch for consistent results.
Transfer the fried calamari onto paper towels, absorbing any excess oil.
Heat your wok or skillet over medium-high heat and add a small amount of oil. Sauté the ginger and garlic for about 30 seconds, just until they start to soften.
Add the chili peppers and continue to sauté until they slightly blister. This will not only reduce the heat but also adds a smoky flavor to them.
Add the fried squid and scallions, then toss them together. Season with more salt and freshly cracked pepper to taste.
Notes
Squid: Small to medium-sized squid tend to be sweeter and more tender. Slice them into thick rings or or cut larger squid into strips, so they cook evenly and brown well without overcooking.
Milk: Use whole milk or other milk products like buttermilk or yogurt diluted with water. Its acidity tenderizes the squid, removes unpleasant odors, and helps the coating adhere better.
Flour: A combination of all-purpose flour and potato flour makes the crunchiest, golden-brown coating that's not too heavy. You can use rice starch or cornstarch in place of potato flour.
Baking powder: It helps make the coating light and crispy.
Pepper: Use Szechuan or Sichuan peppercorns for a more authentic flavor, or just use freshly crackled black pepper.
Chili Peppers: Use jalapeño, serrano, long hot peppers, or Korean peppers. To reduce the heat, remove their seeds and soak them in hot water. For a non-spicy option, shishito peppers will add crunch and color.