Put the cabbage and onion in a heatproof bowl. Heat the vinegar, water, sugar and salt in a small pot over medium heat for about 1 minute, until dissolved. Pour over the cabbage, press the cabbage under the liquid, and leave for at least 30 minutes.

Whisk the buttermilk, hot sauce and 1/2 teaspoon of the seasoning. Add the shrimp and refrigerate for 15 minutes.

In a shallow dish, mix the flour, panko, cornstarch and the remaining seasoning.

Pour oil about 2.5 cm (1 inch) deep into a heavy 28 cm (11 inch) skillet and heat to 175°C (350°F). A breadcrumb should sizzle steadily the moment it hits the oil.

Lift each shrimp from the buttermilk, let the excess drip off, press it into the dredge on both sides and shake lightly.

Fry 6 to 8 shrimp at a time, about 2 minutes per side, until deep golden and crisp. The shrimp should be pearly or white, and opaque, inside.

Lift the shrimp onto a wire rack set over a baking sheet and sprinkle with a pinch of salt. Let the oil return to 175°C (350°F) before the next batch.

Toast the cut sides of the rolls in a dry skillet or the oven for 1 to 2 minutes, until lightly golden.

Tip the pickle into a sieve and press out the extra brine.

Spread the spicy mayonnaise on both halves of each roll. Add lettuce, shrimp, cabbage, jalapeño and cilantro. Close and serve right away.