In a large pot combine 4 cups water, kosher salt, sugar, bay leaf, peppercorns and the halved lemon (squeezed into the pot and then drop halves in). Bring to a gentle boil over medium-high heat.

Poach shrimp

Once liquid is boiling, reduce heat to maintain a gentle simmer. Add shrimp in a single layer and cook just until opaque and firm, about 2 to 3 minutes depending on shrimp size. Jumbo shrimp (16/20) typically take 2.5 minutes. Do not overcook.

Shock shrimp

Immediately transfer shrimp with a slotted spoon to a large bowl filled with ice and the 4 cups ice water to stop cooking. Let chill for 5 minutes until fully cooled.

Peel and chill

If not already peeled, remove shells leaving tails on for presentation. Pat shrimp dry with paper towels and refrigerate until ready to serve on a bed of crushed ice.

Cocktail Sauce

In a medium bowl combine 1 cup ketchup, 3 tsp prepared horseradish, 1 tbsp lemon juice, 1 tsp Worcestershire sauce, 1 tsp hot sauce, 1 tsp salt and 1 tsp black pepper. Whisk until smooth and taste: adjust horseradish for more heat or lemon for brightness. Refrigerate for at least 15 minutes to let flavors meld.

Mustard Aioli

Whisk together 1 cup mayonnaise, 2 tbsp Dijon mustard, 1 tsp whole-grain mustard, 1 tsp lemon juice, 1 tsp minced garlic and 1 tsp olive oil until smooth. Season with 1/2 tsp salt and 1/4 tsp black pepper. Chill at least 10 minutes to mellow the garlic and blend flavors. Taste and adjust salt or mustard as desired.

Garnish & Serve

Arrange crushed ice in a chilled serving platter or individual cocktail glasses. Nestle chilled shrimp over the ice with tails draped over the rim for easy picking.

Spoon cocktail sauce and mustard aioli into small bowls and place alongside the shrimp. Garnish with lemon wedges and chopped parsley. Serve immediately.