Pat the shrimp dry with paper towels. If not already done, peel and devein shrimp leaving tails on or off as you prefer. Season lightly with 1/4 tsp kosher salt and a pinch of black pepper.

Make batter

In a medium bowl combine all-purpose flour, cornstarch, baking powder, the remaining 3/4 tsp kosher salt, and 1/4 tsp black pepper. Whisk to combine. In a separate small bowl whisk the egg with cold club soda (or cold water). Pour the wet into the dry and stir briefly; batter should be slightly lumpy and thick enough to coat shrimp but still runny—add up to 1–2 tbsp extra cold water if too thick.

Heat oil

Heat neutral oil in a heavy skillet or deep pot to 350°F (175°C). If you don't have a thermometer, oil should form bubbles steadily around a small amount of batter and a tossed pea-sized piece should sizzle and rise to the surface in ~30–45 seconds.

Fry shrimp

Working in batches to avoid crowding, dip each shrimp into the batter, letting excess drip off, then gently lower into hot oil. Fry 2–3 minutes per batch until batter is crisp and light golden and shrimp are opaque. Use a slotted spoon to transfer to a wire rack or paper towel–lined tray to drain. Maintain oil temperature between 330–360°F, adjusting heat as needed. Repeat until all shrimp are fried.

Bang Bang Sauce

While shrimp are frying, whisk together mayonnaise, sweet Thai chili sauce, sriracha, honey, rice vinegar, lime juice, garlic powder, and 1/8 tsp kosher salt in a bowl until smooth and homogenous. Taste and adjust: add up to 1 tsp more sriracha for heat or 1–2 tsp more sweet chili sauce for sweetness. If sauce is too thick, thin with 1–2 tsp warm water.

Reserve about 2 tbsp of the sauce per serving as a dipping sauce if desired; place the remainder in a shallow bowl or large mixing bowl to toss with hot shrimp.

Garnish & Serve

Crisp shishito peppers

While shrimp finish frying, heat a small nonstick or cast-iron skillet over medium-high. Add 1 tsp neutral oil, add the shishito peppers in a single layer and cook, shaking or turning occasionally, until blistered and softened in spots, about 3–4 minutes. Sprinkle with a small pinch of salt and remove.

Toss shrimp in sauce

When all shrimp are hot and drained, place them in the shallow bowl with the majority of the bang bang sauce. Gently toss until shrimp are evenly coated — do this quickly so the fried coating remains crisp. Alternatively, spoon sauce over shrimp on a serving platter.

Plate and finish

Arrange coated shrimp on a platter or individual plates. Scatter blistered shishito peppers around or on top. Sprinkle toasted sesame seeds and sliced scallions over the shrimp. Serve immediately with lime wedges and reserved dipping sauce on the side.