Pat shrimp dry with paper towels. Lightly season both sides with 0.25 tsp salt and 0.125 tsp black pepper. Let sit while you prepare the batter (5 minutes).

Make batter

In a medium bowl, whisk together 3 tbs all-purpose flour, 2 tbs cornstarch, 0.5 tsp baking powder and 0.5 tsp salt. Slowly whisk in 1/2 cup cold sparkling water until just combined; batter should be slightly lumpy and thin enough to coat (adjust with a splash more water or 1 tbs flour if needed). Keep batter cold in the refrigerator for 5 minutes.

Fry shrimp

Heat 1 cup vegetable oil in a deep skillet or small pot until it reaches 350°F (175°C) or a wooden skewer bubbles steadily when inserted. Working in a single layer, dip each shrimp into the batter to coat, letting excess drip off, then carefully add to the hot oil. Fry 2–3 minutes until golden and just cooked through. Remove with a slotted spoon to a wire rack or paper towel-lined plate. If your pan is shallow, use the 1/2 cup neutral oil and shallow-fry in batches, turning once, 2–3 minutes total. Keep warm in a 200°F (95°C) oven while you finish other components.

Squeeze a little lemon over fried shrimp just before plating.

Cucumber Base

Trim ends of the English cucumber. Slice on a slight diagonal into 1/4- to 1/3-inch rounds or create 1/2-inch thick oblique slices for small boats. Place slices in a bowl and toss with 1 tbs rice vinegar, 1/2 tsp sugar and 1/4 tsp salt. Let sit 5–10 minutes to lightly pickle and remove excess water; blot any moisture with a paper towel before assembling so the topping doesn't get soggy.

Special Crab Mix (topping)

In a bowl, combine 150 g finely chopped imitation crab or lump crab, 3 tbs mayonnaise, 1 tsp chili sauce (adjust to taste), 1 tsp masago or tobiko if using, 1 tbs thinly sliced scallion, 0.5 tsp sesame oil, 0.5 tsp lemon juice, 1/8 tsp salt and a pinch (1/16 tsp) of black pepper. Fold gently until everything is evenly coated. Taste and adjust seasoning — add more mayo for creaminess, more chili for heat, or more lemon for brightness.

Garnish & Assembly

Arrange the quick-pickled cucumber slices on a serving platter or individual plates, leaving small gaps for the fried shrimp. Spoon a generous teaspoon to tablespoon of the special crab mix onto each cucumber slice, depending on cucumber size. Place one fried shrimp on top of each crab-topped cucumber (tail can be left pointing up for presentation).

Finish with a sprinkle of toasted sesame seeds, 2 tbs microgreens or chopped cilantro distributed across the bites, and thin slices of jalapeño if using. Serve immediately while shrimp are hot and crispy.