In a large pot, combine 8 cups water, 1 tablespoon kosher salt, the juice of half the lemon (reserve the half for serving), the squeezed lemon half plus the rind, 2 bay leaves, 8 black peppercorns and 2 tablespoons of chopped fresh parsley (optional). Bring to a gentle boil over high heat.

Poach shrimp

Once the liquid reaches a rolling boil, reduce heat so the liquid is at a brisk simmer. Add the shrimp in a single layer and return liquid to a gentle simmer. Poach until shrimp turn pink, opaque and curl into a loose C — about 2 to 3 minutes depending on size. Do not overcook.

Shock and chill

Prepare a large bowl with 4 cups of ice and 2 cups cold water to make an ice bath. Using a slotted spoon, transfer shrimp immediately into the ice bath to stop cooking. Let chill for 5 minutes until completely cold. Drain well and pat dry with paper towels. Refrigerate shrimp until ready to assemble (can be kept chilled for up to 24 hours).

Chopped Cocktail Sauce

In a small bowl, combine 3 tablespoons ketchup, 1 teaspoon prepared horseradish, 1 teaspoon Worcestershire sauce, 1 teaspoon fresh lemon juice, and 1 teaspoon hot sauce. Stir to incorporate.

Fold in 1 tablespoon very finely chopped shallot, 1 teaspoon finely chopped capers, and 1 teaspoon finely chopped fresh parsley. Season with 1 teaspoon salt and 1/4 teaspoon black pepper. Taste and adjust: add more horseradish for heat, more lemon for brightness, or a bit more ketchup to mellow. Chill the sauce at least 15 minutes to let flavors meld.

To Serve

Arrange chilled shrimp on a platter around a small bowl of the chopped cocktail sauce (or portion into individual cups). Garnish with lemon wedges and parsley sprigs. Serve immediately, allowing guests to squeeze additional lemon over shrimp and dip into the sauce.