1 Make the bang bang sauce: In a bowl, whisk the mayonnaise, chili garlic sauce, and sriracha together until blended. Store up to two days in the refrigerator until ready to use.
2 Marinate the shrimp: In a separate bowl, marinate the shrimp in the buttermilk for 20 minutes.
3 Prepare your breading station: Combine the flour, cornstarch, salt, and pepper in a medium bowl.
Set a cooling rack on top of a sheet pan on which to place the breaded shrimp prior to frying (this helps achieve a crispy coating on the shrimp).
Set up a draining station as well by lining another sheet pan with a thick layer of paper towels. (Or, if you have another cooling rack to set over the sheet pan, that’s even better!)
Set the oven to 200°F.
4 Bread the shrimp: While the oil heats, drain the buttermilk and toss the shrimp, in batches, in the flour mixture. Shake off any excess flour and arrange the shrimp on the cooling rack to “dry out” while you’re heating your frying oil.
5 Heat the oil: Place a thermometer in a wide, deep pot, such as a Dutch oven, and add the oil. Heat over medium-high heat until the oil reaches 350°F. (This will take about 20 minutes.)
6 Fry the shrimp: Add a handful of the shrimp to the hot oil, and after a minute of frying, use a slotted spoon to stir and separate the shrimp; they like to stick together. Fry for 4 to 4 1/2 minutes, or until the shrimp are golden brown.
7 Keep the shrimp warm and continue frying: Remove the shrimp from the oil with a slotted spoon and place them on your draining rack/pan. Place the cooked shrimp in the warm oven.
Continue frying the remaining shrimp in batches. Remember to let the oil come back up to 350°F in between batches.
8 Sauce the shrimp: Once all of the shrimp has been fried, toss it all in 1 cup of the sauce. Reserve the remaining sauce for drizzling on top of the tacos.
9 Assemble the tacos: Fill the warmed tortillas with a handful of shredded cabbage, then top the cabbage with the shrimp, then more sauce (if desired). Garnish the tacos with sliced radishes, jalapeños, green onions, and the chopped cilantro, then serve.
These tacos are best enjoyed right away.