In a large saucepan combine 3 cups water, 1 cup white wine (optional), 1 tablespoon kosher salt, 8 peppercorns, 1 bay leaf and the halved lemon (cut side down). Bring to a gentle simmer over medium heat — do not boil vigorously.

Poach shrimp

Add the shrimp in a single layer. When the liquid returns to a gentle simmer, cook shrimp 2 to 3 minutes until they turn pink and curl but are still slightly translucent at the thickest part. Cooking time depends on shrimp size; avoid overcooking.

Shock and chill

Immediately transfer shrimp to a bowl of ice and 4 cups ice water to stop cooking. Leave until shrimp are completely chilled, about 5 minutes. Drain and pat dry with paper towels. Keep refrigerated until serving.

Cocktail Sauce

In a medium bowl combine 1 cup ketchup, 2 tablespoons prepared horseradish, 1 tablespoon fresh lemon juice, 1 teaspoon Worcestershire sauce, and 1 teaspoon hot sauce if using. Season with 1 teaspoon salt and 1/4 teaspoon black pepper. Taste and adjust horseradish, lemon, or hot sauce for desired heat and brightness. Refrigerate at least 15 minutes to let flavors meld.

Dijonnaise

Whisk together 1/2 cup mayonnaise, 2 teaspoons Dijon mustard, 1 teaspoon lemon juice, and 1 teaspoon olive oil until smooth. Season with 1/4 teaspoon salt and 1/8 teaspoon black pepper. Adjust mustard or lemon to taste. Chill until serving.

Garnish & Assembly

Arrange chilled shrimp on a platter or individual cocktail glasses over ice. Spoon cocktail sauce into a small bowl or into the center of each serving. Place dijonnaise in a second small bowl. Provide extra prepared horseradish (1 teaspoon) for guests who want more heat.

Garnish with lemon wedges and sprinkle chopped parsley over the platter. Serve immediately, letting guests dip shrimp into cocktail sauce or dijonnaise and squeeze lemon as desired.