Pat shrimp dry with paper towels. Place shrimp in a bowl and pour the buttermilk over them. Toss to coat and let sit 10–15 minutes while you prepare the coating. This tenderizes and helps the coating adhere.

Make dry mix

In a shallow bowl or pie plate, whisk together the all-purpose flour, cornstarch, baking powder, kosher salt, black pepper, and paprika until evenly combined.

Sauce

While shrimp are marinating, make the boom boom sauce. In a medium bowl combine the mayonnaise, sweet chili sauce, Sriracha, honey, rice vinegar, soy sauce, grated garlic, lime juice (if using), sesame oil, salt, and black pepper. Whisk until smooth and taste; adjust heat or sweetness to preference. Refrigerate until ready to use (can be made several hours ahead).

Frying

Heat the oil in a deep heavy-bottomed pot or Dutch oven to 350°F (175°C). Use a thermometer for accuracy. There should be at least 2–3 inches of oil to allow the shrimp to float while frying.

Working in batches of 6–8 shrimp (do not overcrowd), remove shrimp from buttermilk, allowing excess to drip off, then dredge each shrimp in the dry flour mixture, pressing lightly so the coating adheres. Shake off excess.

Carefully lower dredged shrimp into the hot oil. Fry 2–3 minutes until golden brown and crisp and shrimp are opaque (internal temperature 120–130°F/49–54°C). Flip once if needed for even browning. Remove with a slotted spoon and transfer to a wire rack set over a baking sheet or paper towels to drain. Repeat with remaining shrimp. Keep cooked shrimp warm in a 200°F (95°C) oven if needed.

Toss & Serve

Place the warm fried shrimp in a large bowl. Add the boom boom sauce a little at a time (start with about 3–4 tablespoons for 24 shrimp), tossing gently to coat each piece evenly. Add more sauce to taste—aim for a glossy, lightly coated finish (you may not need all the sauce).

Transfer coated shrimp to a serving platter. Sprinkle with sliced green onions and toasted sesame seeds. Serve immediately with lime wedges on the side for squeezing over.

Leftover sauce: keep refrigerated in an airtight container for up to 5 days.