Rinse the shrimp and pat dry with paper towels. Season with 1 tsp kosher salt, 1/2 tsp black pepper and 1 tbsp lemon juice; toss to coat. In a medium pot fitted with a steamer basket, bring 2 cups water to a simmer. Place shrimp in the basket in a single layer, cover, and steam over simmering water until opaque and just cooked through, 3–5 minutes depending on size. Transfer shrimp to a bowl and set aside to cool slightly.

Spicy aioli

Make aioli

In a small bowl combine 1/2 cup mayonnaise, 1 tbsp Sriracha, 1 tsp gochujang (or extra Sriracha), 1 tbsp lime juice, 1 tsp rice vinegar, 1/2 tsp sesame oil, 1 minced garlic clove, 1/2 tsp honey, 1/4 tsp salt and 1/8 tsp black pepper. Whisk until smooth and taste; adjust heat or acidity to preference. Refrigerate until ready to serve. Reserve a small spoonful for drizzling and another for tossing if desired.

Cucumber & garnish

Quick-pickle cucumber

Trim and thinly slice 1/2 English cucumber on a mandoline or with a knife. In a small bowl stir together 2 tbsp rice vinegar, 2 tbsp water, 1 tsp sugar and 1/4 tsp salt until dissolved. Add cucumber slices and toss to coat. Let sit 10–15 minutes, then drain off excess liquid and reserve a few pickled slices for plating.

Prepare garnishes

Toast 1 tbsp black sesame seeds in a dry skillet over medium heat for 1–2 minutes until fragrant; cool. Thinly slice scallions and set aside. If using microgreens or cilantro, rinse and pat dry.

Tempura crunchies

Make and fry crunchies

Heat 1 cup vegetable oil in a small heavy-bottomed saucepan to 350°F (175°C) or until a small piece of batter sizzles immediately. In a bowl whisk together 1/2 cup tempura mix (or all-purpose flour), 1 tbsp cornstarch, and 1/8 tsp baking soda. Add 1/2 cup ice-cold sparkling water and stir once or twice; batter should be lumpy and very cold (do not overmix). Using a fork, flick or drizzle small amounts of batter into the hot oil to create irregular 'crunchies' — work in batches. Fry until pale golden and crisp, about 30–60 seconds. Remove with a slotted spoon to paper towels and immediately season with 1/4 tsp salt. Allow to cool; they will become extra crisp as they rest.

Assembly & serve

If desired, toss the slightly warm shrimp with 2–3 tbsp of the spicy aioli to coat lightly (optional). Arrange shrimp on a serving platter or individual plates. Nestle pickled cucumber slices alongside or under the shrimp. Spoon small dollops of remaining aioli across the plate or drizzle with a squeeze bottle. Scatter tempura crunchies over the shrimp and around the plate for texture. Sprinkle toasted black sesame seeds and sliced scallions over the dish, and finish with microgreens or cilantro if using. Serve immediately so crunchies remain crisp.