Batter-fried fish tacos as we know them in the United States originated in the 1930s in Ensenada, Mexico, home to a large Japanese immigrant population who worked in the fishing industry there. Along with their skills as fishermen, the Japanese also brought with them the technique for tempura—deep-frying fish in batter. The Mexicans adapted this technique to make tacos, using young shark, a very inexpensive local catch that held up beautifully when fried. These tacos are best served immediately as fried foods get soggy if left to sit. If you can’t find shark, substitute a firm, moist white fish like wahoo, tilapia, or mahi mahi.