In a medium saucepan large enough to hold the prawns in a single layer, combine 6 cups water, 1 tablespoon kosher salt, 1 bay leaf, 6 peppercorns and the halved lemon (squeeze one half into the water, then add both halves). Bring to a simmer over medium-high heat until it just reaches a gentle boil.

Poach prawns

Add the black tiger prawns to the simmering liquid in a single layer. Return to a gentle simmer and cook until the prawns turn opaque with pink shells and curl into a loose 'C' — about 2 to 3 minutes for large prawns. Do not overcook (tight 'O' shape indicates overcooking).

Shock and chill

Using a slotted spoon, transfer the prawns immediately to the prepared ice bath to stop cooking. Let chill for 3 minutes until completely cool. Drain well and pat dry with paper towels. If desired, remove shells and leave tails on for presentation, or serve fully peeled.

Cocktail sauce

In a small bowl combine 3 tablespoons ketchup, 1 tablespoon prepared horseradish, 1 teaspoon fresh lemon juice, 1 teaspoon Worcestershire sauce, 1 teaspoon hot sauce, 1 teaspoon smoked paprika and 1 teaspoon Old Bay (or celery salt). Whisk until smooth and taste; adjust heat by adding more horseradish or hot sauce, and balance sweetness/acidity with a bit more lemon if desired.

Stir in freshly ground black pepper and the optional 1 tablespoon finely chopped parsley for a bright finish. Refrigerate the sauce at least 10 minutes to let flavors meld if time allows.

To serve

Arrange chilled prawns on a platter over a bed of crushed ice if desired, with a small bowl of cocktail sauce in the center. Garnish with lemon wedges and parsley sprigs or microgreens. Serve immediately so prawns remain cold and firm.

Leftovers: store prawns and sauce separately in airtight containers in the refrigerator for up to 2 days.